13.8: How Important Is The Packaging?
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“Imitating paper on a computer screen is like tearing the wings off a 747 and using it as a bus on the highway.” (Ted Nelson, 1999) The final step of the planning process is a fundamental and critical one: choosing the packaging of the course.
There are a variety of elements that are important in this process including the general content structure, sequence, flow, and pacing. Presentation structure is also important, and includes considerations such as the tone and mood projected in the text and ‘feel’ of the site, including the coherence, consistency, navigation, aesthetic use of colours and graphics, and the text fonts used in the overall course site interface. The important components are discussed in the following section.
Units of Study
A uniform approach to presenting the units of study not only makes sense, but helps reinforce learning. A common mode of organization is a hierarchical module—sections—lessons—supportive activities approach. Within each learning activity, uniformity also helps to guide students through the content. One easy way to organize the units is from general to specific, beginning with units focused on basic principles then working up to unique and specific content topics. For example, a course on research design might begin with units focused on the general research process, literature searches and the like, then move on to specific research design processes such as experimental quantitative design or phenomenological qualitative methods.
Structure
A consistent structure should be used to present the units of study. Information, help, resource, and other sections need to be positioned in the same area of the page, across screens and sections. The generous use of white space helps to keep this structure accessible and visually appealing for the learners. The learning activities should also have a consistent structure. One common method is to use a lesson template including such headings as Overview, Objectives, In Preparation, Class and Individual Activities, Reflection, Enrichment Activities or Resources, and References.
The back-end structure that supports the learner environment should be carefully thought out as well. Folders or databases are needed for each group or cluster of files. A common practice is to group all images in an image database or folder; all multimedia in a multimedia database or folder; all audio in a separate folder, and so on. This not only helps the instructor find necessary components, but also facilitates upgrades and editing, and facilitates downloading and uploading of files from the course website.
Sequence
A plan to present all content and activities in a sequential flow is important to ensure learners have instant access to current and archived content, and do not miss critical pieces. Sequencing would follow the units of study and structure determined beforehand, moving from general to specific. This sequencing is best viewed as a specific menu or site map, where students can get a view of the entire course content on one screen.
Flow
Flow is achieved by presenting the sequential content in an intuitive yet logical manner. It is also boosted by clear, consistent navigation and positioning of screen elements. The learner should immediately know where to go next, without confusion or resorting to trial and error clicking on various navigation buttons or titles.
Pacing
It is best to keep the text areas small, so that the course content is presented in chunks, limiting the amount of text that is presented on each screen. Short lines of 40 to 60 characters each are best. The use of tables, charts, bulleted lists, and other organizers help to increase the visible appeal and reinforce learning. If possible, avoid long vertical scrolling pages; at all costs.
Tone
The design team should find ways to present help files, course content, and other textual prompts using an active voice, second person, present tense and a conversational tone in the course design. Language should be concise and consistent. It is also best to avoid language and examples that will inhibit the “shelf-life” of the site, such as “Now in 2008 …”.
Coherence
The design team should ensure that the layout of each screen is clear, pleasing to the eye, and conforms to the Western text layout of left-to-right, top-to-bottom text standards, since this is how learners usually read. It can be very confusing if their eyes need to dart all over the screen to understand what is before them: this can cause both dissonance and confusion.
Consistency
It is important to keep the general layout design of the course screens consistent in size, structure, colour, placement of elements and font usage. It is also important to make sure that the appearance and utility of the site is consistent across browsers (e.g., the site should look and act the same in Internet Explorer and Firefox). Efforts should be made to facilitate download and screen loading times across Internet access modes, including broadband and dial-up access. This means keeping the size of graphic, audio, multimedia, and text files compact and reasonable in size, and optimized for quick loading and downloading. As well, learners should be able to upload files to the course area within a few seconds, and without crashing their systems or freezing the web browser screen.
Navigation
Navigation online is like the nervous system of the human body. It connects all of the course elements, allowing movement and flow as the learners explore the course. The key to designing navigation is to pick one uniform method, and stick to it consistently throughout the course site. Navigation can be as simple as a set of uniform buttons placed strategically in the same place on every page. Or it can consist of Java based panels or animated Flash “hot spots” on an image map.
Graphical menus and navigational elements help to intuitively guide the learner through the course online environment. It is best to plan the navigation to give the learner control over what sections they can select for navigation but to also provide a “road map” with suggested navigation sequences. Navigational linked sections should somehow be distinguishable from static non-linked portions of the site (for instance, use a different colour, specific icons, underlining, or roll-over text changes). Consistency in navigation is important to reduce learner frustration and to maximize the learning experience. Navigation buttons should be clearly labelled, consistent across pages, and easy to view and access.
Colour
“Color is born of the interpenetration of light and dark”. (Sam Francis, 2003)
Colour is an important feature of effective course design. First off, it is best to choose colours that are included in the 216-colour cross-browser platform colour palette. Although this precaution is becoming less critical, since the majority of modern computers will support millions of colours, it is safe to stick to this rule to ensure that the learners will be able to access the general 256 colour palette common on most computers made within the past ten years or so.
Colours on the Web are always a mixture of R (Red), G (Green) and B (Blue). The R or G or B value can range from 0 to 255, with 0 meaning the colour value (e.g., the R) is off, and 255 meaning the value is fully on. Every screen colour has a value that tells the designer how much of the R, G, and B is showing or absent. In website development, red, green, and blue values are written as six-digit hexadecimal coding: a combination of numbers from 0 to 9 and letters from A to F. For example, pure blue has a hexadecimal value of 0000FF, and so on. To ensure that the colours are visible as intended, it is wise to stick to the web-safe palette of hues. This is because browser-safe colours don’t dither. Dithering is what happens when a colour is not available in the web palette, so the browser tries to compensate by combining pixels of other colours to substitute. Dithered colours look rough and spotty: browser-safe colours stay smooth and even looking.
Colour is also a very important consideration to set the mood, tone, and visual appeal of a course site learner interface. If it is possible to customize the colour scheme for each course, spend time as a team to visualize the landscape or metaphor that is suggested by the course content. For instance, a general biology course might suggest the use of greens offset with browns and white; while a course on metaphysics might suggest the use of purples, lilacs, rich blues offset with white. If you want to wake up your learner audience, to initiate action or stimulate emotions, a warm colour scheme works best. Reds, oranges, yellows all do the trick. If your intended mood is one of calm, leisure, or dignified refinement, use cooler colours—blues, purples, greens. If your statement is bold and to the point, sharp contrasting colours such as black and white or blue and orange work well.
Basic colour theory
Colour theory focuses on how colour manifests on the spectrum. Colour psychology goes one step further to assign common meaning or moods to specific colours. To apply these to the course design, the team should explore the meaning of primary, secondary and tertiary colours which are the most common colours used on the World Wide Web. Figure \(\PageIndex{1}\) illustrates the 12 basic colours of the colour wheel.
Primary colours are the three pigment colours that cannot be mixed or formed by any combination of other colours. All other colours are derived from these three: red, blue and yellow. Each of these pure colours stir up different moods and feelings in a viewer. Figure \(\PageIndex{2}\) illustrates the primary colours.
- Red—hot, fire, daring, lush, aggressive, power, excitement, dominating, warning.
- Blue—peaceful, water, calm, wisdom, trust, loyalty, dedication, productivity.
- Yellow—happy, sunny, cheerful, alert, concentration, bright, warm, creative, playful.
Secondary colours are formed by mixing two of the primary colours together. These mixed colours also evoke particular moods. Figure \(\PageIndex{3}\) illustrates the secondary colours from the mixture of two primary colours.
- Green (blue and yellow)—pastoral, spring, fertility, jealousy, novice, youth, hope, life, money
- Orange (red and yellow)—warm, autumn, generous, strong, fruitful, appetizing
- Purple (red and blue)—royal, mysterious, pride, luxury, wealth, sophistication
Tertiary colours are formed by mixing the secondary colours with primary colours. The olour wheel, illustrated in Figure \(\PageIndex{1}\) gives examples of the six tertiary colours between the three primary and three secondary colours.
- Yellow-orange
- Red-orange
- Red-purple
- Blue-purple
- Blue-green
- Yellow-green
Analogous colours are any three colours which are side by side on a 12-part colour wheel. Complementary colours are any two colours which are directly opposite each other, such as red and green.
Of course there are also black and white, both very common colours used in course designs.
Black is the absence of red, blue, and green light while white is the purest saturation of all three. Black and white plus gray are known as non-chromatic hues.
- Black represents style, dark, mystery, formal, powerful, authority.
- White is clean, pure, chastity, innocence, cool, refreshing.
- Gray is neutral, conservative, formal colour. Gray ranges from sophisticated charcoal gray to active, energizing silver. It also represents maturity, dependability, and security.
Fonts
Finally, text fonts and embellishments can be used to help improve the comprehensiveness, presentation and accessibility of the content. Use a consistent font (common ones include two sans serif fonts: Arial and Verdana, and two serif fonts, Times New Roman and Georgia) throughout the text. Figure \(\PageIndex{6}\) shows examples of these four common fonts. Use bold and italic embellishments for emphasis. Only use underlines for actual links. Avoid using all capital letters. A good rule of thumb is to use size 11 for general text font, 14 for subheadings, 16 for titles. It is best to avoid blinking text, as this can produce eye fatigue and may annoy the learners. As well, graphical dingbat fonts can be used to create icons, and other supportive graphics (Figure \(\PageIndex{5}\)).


15.8H: Campylobacter
- Discuss the method of transmission for Campylobacter
Description of Campylobacter Bacteria
Campylobacter is a genus of bacteria that are Gram-negative, spiral, and microaerophilic. The name means “twisted bacteria” because of the spiral formation; motile, with either unipolar or bipolar flagella, the organisms have a characteristic spiral/corkscrew appearance and are oxidase-positive.
Campylobacter jejuni is now recognized as one of the main causes of bacterial foodborne disease in many developed countries. At least a dozen species of Campylobacter have been implicated in human disease, with C. jejuni and C. coli the most common. C. fetus is a cause of spontaneous abortions in cattle and sheep, as well as an opportunistic pathogen in humans.
Campylobacter species contain two flagellin genes in tandem for motility: flaA and flaB. These genes undergo intergenic recombination, further contributing to their virulence. Nonmotile mutants do not colonize.
Methods of Transmission and Treatment
The common routes of transmission are fecal-oral; the bacteria are introducted through ingestion of contaminated food or water and by the eating of raw meat. Infection produces an inflammatory, sometimes bloody diarrhea, periodontitis, or dysentery syndrome, mostly including cramps, fever and pain. The infection is usually self-limiting. In most cases symptomatic treatment by liquid and electrolyte replacement is enough in human infections. The use of antibiotics, on the other hand, is controversial.
Diagnosis
Symptoms typically last for five to seven days. The sites of tissue injury include the jejunum, the ileum, and the colon. Most strains of C. jejuni produce a toxin (cytolethal distending toxin) that hinders the cells from dividing and activating the immune system. This symptom helps the bacteria evade the immune system and survive for a limited time in the cells. A cholera-like enterotoxin was also once thought to be made, but this appears not to be the case. The organism produces diffuse, bloody, edematous, and exudative enteritis. Although rarely has the infection been considered a cause of hemolytic uremic syndrome and thrombotic thrombocytopenic purpura, no unequivocal case reports exist. In some cases, a Campylobacter infection can be the underlying cause of Guillain-Barré syndrome. Gastrointestinal perforation is a rare complication of ileal infection.
Diagnosis of the illness is made by testing a specimen of faeces (bowel motion). Standard treatment is now azithromycin and, on occassion, terbinafine. Quinolone antibiotics such as ciprofloxacin or levofloxacin are no longer as effective due to resistance. Dehydrated children may require intravenous (by vein) fluid treatment in a hospital. The illness is contagious, and children must be kept at home until they have been clear of symptoms for at least two days. Good hygiene is important to avoid contracting the illness or spreading it to others.
Key Points
- Campylobacter jejuni is now recognized as one of the main causes of bacterial foodborne disease in many developed countries.
- The common routes of transmission are fecal-oral, ingestion of contaminated food or water, and the eating of raw meat.
- It produces an inflammatory, sometimes bloody, diarrhea, periodontitis or dysentery syndrome, mostly including cramps, fever and pain.
Key Terms
- microaerophilic : living and thriving in an environment low in oxygen
- enteritis : Inflammation of the intestines, generally the small intestine, that may lead to diarrhea.
- flagella : A flagellum is a lash-like appendage that protrudes from the cell body of certain prokaryotic and eukaryotic cells.


Although Karen Horney was the first female psychoanalyst to openly challenge Sigmund Freud’s theories regarding the psychology of women, she abandoned this line of work when she came to the conclusion that culture was a more significant issue than gender in determining the psychology of women. Of course, that decision is based on separating gender from culture, which is not something that everyone would agree with. In the 1970s, the Stone Center was established, as a group of pioneering women began the work that led to a theory on the personality development and psychology of women based on a combination of seeking and forming relationships within a cultural context. This work continues today, and the theory is being expanded to include the personality development of all people, women and men.


14.4: Chapter Summary
This chapter covered what pain is, how the brain perceives it, and how medications are commonly used to treat it. Because the nature of pain is subjective, different ways to assess a client’s pain were explained. The concept of the pain threshold and factors that can affect it were described.
Drug classes covered in this chapter include the nonopioid analgesics, opioid agonists, and opioid antagonists. Common nonopioid analgesics include many over-the-counter medications such as acetaminophen and NSAIDs as well as tramadol. Potential serious adverse effects of opioid agonists and the risk for tolerance and addiction were explained as well as the potential for opioid antagonists to induce opioid withdrawal.


19.4: Indigenous Agency and Rights
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- Jennifer Hasty, David G. Lewis, & Marjorie M. Snipes
- OpenStax
Learning Objectives
By the end of this section, you will be able to:
- Explain the significance of Indigenous peoples being declared “domestic dependent nations” in the United States.
- Discuss Indigenous rights to natural resources and the degree to which Native nations have been successful in asserting these rights.
- Describe some traditional techniques used by Indigenous peoples to create cultural objects as well as efforts to restore this knowledge.
- Articulate two features of Indigenous philosophies and worldviews and explain how researchers access Indigenous philosophies and worldviews.
- Describe political responses to federal government policies pertaining to Indigenous peoples in the United States.
- Articulate Indigenous critiques of the use of Indigenous names and images as mascots for sports teams.
Treaties and Removal
In the mid-19th century, the United States federal government shifted its approach toward purchasing tribal lands rather than conquering Indigenous nations. Many Native societies had already suffered greatly due to White settlement and were ready to sign treaties that would guarantee them protection on federal Indian reservations . Population loss caused by epidemic disease also played a role in many tribes’ decisions to sign treaties with the federal government. Those who signed treaties received payment for lands, money for schools, and support in establishing Western farming practices in addition to land allotments on a reservation where federal authorities were to guarantee their safety.
As White settlement expanded into the western United States, Indigenous peoples both on and off federal reservations were subject to waves of removal from their lands. Areas set aside for reservations that had once seemed undesirably remote for White settlement became increasingly desirable as the White population grew. In the 1830s, tribal peoples living on reservations east of the Mississippi River were forced to move to what is now Oklahoma, then called Indian Territory. The tribes were promised that they would be able to keep their new reservation lands in perpetuity. However, when political currents changed, largely due to the pressures of European immigrants moving westward who desired land for settlement, the land formerly designated Indian Territory was opened to White settlement, and reservations diminished.
The most famous Native removal was the Cherokee Trail of Tears in 1838. After President Andrew Jackson signed the Indian Removal Act in 1830, the US Army forced an estimated 16,000 Cherokee then living in the southeast United States to walk to Indian Territory. An estimated 5,000 of these people died on the trail. The Cherokee Trail of Tears was not the only removal. Each time the United States expanded its borders into Indian Territory, tribes were forced to move to smaller reservations with less desirable, resource-poor lands. The Choctaw were removed from Florida to Oklahoma in 1831, and the Creek were removed in 1836, leading to an estimated 3,500 of their 15,000 people dying. Twenty years later, the United States assumed sole title to the lands of the Oregon Territory and removed 4,000 Native people from some 60 different tribes onto two reservations, the Coast and Grand Ronde Reservations. During the western Oregon “Trails of Tears,” members of tribes then living on the temporary Table Rock and Umpqua Reservations were forced to walk more than 300 miles in the dead of winter to the Coast and Grand Ronde Reservations, with many dying from exposure. Once at the Coast and Grand Ronde Reservations, the tribes were made to live with many other tribes from five different language families and to join as one tribe on the reservations.
In all parts of the United States, life on the reservations was very challenging. Native peoples had to build their own houses and establish means of producing food and other necessities with limited resources. Federal aid, although guaranteed in the treaties, was slow to arrive and sometimes lost in transit or simply missing. For the first 20 years of the Grand Ronde Reservation, residents lived in poverty with inconsistent food and health care and poorly planned schools. On Oregon reservations, the tribal peoples did not receive their treaty rights of individual plots of farmland until at least 1873. While the government had guaranteed food, by 1860, it was clear that federal officials could not be counted on for regular food shipments. Thousands of Native people died at early ages in the first two decades due to malnutrition and newly introduced diseases. Similar stories can be told for all tribes in the United States. Problems were also caused by untrained, unqualified, and corrupt government officials who stole food, money, and supplies.
Domestic Dependent Nations
The legal status of Native nations was greatly influenced by several paternalistic rulings by the US Supreme Court in the 1830s. Three rulings known as the Marshall court trilogy ( Johnson v. M’Intosh , 1823; Cherokee Nation v. Georgia , 1831; Worcester v. Georgia , 1832) determined that tribal peoples were domestic sovereign nations within the United States and dependent on the federal government to guarantee their sovereignty. These rulings meant that all reservations were “federal lands,” not part of the states, with the federal government as the administrator. Native rights, therefore, must be given through federal authorities or named in treaties with the federal government.
This state of dependency has caused much consternation among Native peoples ever since. As “domestic dependent nations,” many aspects of tribal societies—including management of money, land, education, health care, and other programs—have been administered by the federal government. Beyond the question of the appropriateness of this arrangement, there have been innumerable documented cases of Native peoples not receiving the services or funds they were promised. Between 1910 and the 1980s, Native peoples filed hundreds of civil cases against the federal government for mismanagement of service, land, and money. By the 1940s, there were so many cases that the federal government established a special jurisdictional court, the Indian Claims Commission, to deal with the volume of lawsuits. Under the Indian Claims Commission, many cases were consolidated to make the process more efficient. Originally planned to exist for 10 years, the court was extended into the 1970s, as hundreds of cases had been filed and it was taking decades to decide many of them. The Klamath tribe, for example, filed seven Indian Claims lawsuits for mismanagement of the money they earned through logging operations. The Klamath cases were combined and decided in the 1950s, with some payouts from their lawsuits extending into the 1960s. The Indian Claims Commission ended in 1978, having cleared 546 dockets and named 342 awards totaling $818,172,606.64.
One example of a successful Indian Claims case (number K-344) involved California tribal members of groups called the Mission Indians and other tribes from Northern California. These tribes had signed 18 treaties with the federal government in 1851. The treaties were never ratified, and as such, the tribes were never paid for their lands. After the treaties were found hidden in the vast record collections of the National Archives in 1905, the California tribes began working on a case for payment for the lands, for which they filed suit in 1928. The first case was not decided until 1942, with the court declaring that “the Indians of California consist of wandering bands, tribes, and small groups, who had been roving over the same territory during the period under the Spanish and Mexican ownership, before the [1848] treaty between Mexico and the United States whereby California was acquired by the United States” (Indians of California ex rel. U. S. Webb v. United States, 98 Ct. Cl. 583, 1942) This decision meant that the tribes were determined not to have a case for the return of lands and could only ask for cash payments. A second case was decided in 1964. Payments from both cases did not come until 1969, when the court gave the tribes 47 cents per acre for the 64 million acres of California lands they had once occupied, a total of $29.1 million. Court awards were subject to political maneuvering and arbitration within the House of Representatives over how much the tribes would actually receive. In the case of K-344, the award amount was based on the value of the lands in 1851, which had skyrocketed in value over the more than a century that had passed. Many tribal members were very upset by the paltry sum awarded for the wealthy lands of California.
Water, Fishing, and Agency
From the 1960s to the 1980s, an issue of particular concern to the tribes of the northwestern part of the United States was fishing rights. The “fishing wars” were a series of political and legal battles over whether Indigenous peoples had the right to fish in their usual and accustomed places, as promised in numerous treaties. Following the Belloni ( Sohappy v. Smith/United States v. Oregon , 1969) and Boldt ( United States v. Washington , 1974) court decisions, the tribes of Washington State, including those that had been terminated and not yet restored, maintained their rights to fish in their usual and accustomed ways—and their right to half the catch in the state of Washington.
These decisions affirmed tribal sovereignty rights promised in ratified treaties but had the negative consequence of causing delays in the restoration of other tribes from termination. Many sport fishermen’s organizations feared that an increase in restored tribes would impact fishing for non-Natives. Both the Siletz and Grand Ronde tribes experienced delays related to fears about fishing in their federal restorations in the 1970s and 1980s. Ultimately, both tribes were forced to give up fishing and hunting rights to become federally restored. Ironically, neither the Grand Ronde nor the Siletz have fishing or hunting rights in their ratified treaties. Both tribes concluded that restoration of the tribal governments was more important than holding out for fishing and hunting rights.
The Klamath tribe of Oregon was terminated in the 1950s, along with tribes in California, including the Karuk and Yurok, all of whom traditionally relied on fish from the Klamath River. In the 1970s and 1980s, these tribes were restored by the US federal government with their rights intact. The Klamath tribe of Oregon is the only tribe on the river with a ratified treaty that guaranteed fishing rights. During the termination period, the federal government had built numerous dams and water reclamation projects on the river and given away water resources to farmers and ranchers in the area. Dams such as the Shasta Dam had destroyed many salmon runs, and the water giveaways had taken much-needed in-stream flows out of the river, making the river warmer and less environmentally friendly to fish. When local tribes were restored, they began demanding rights to fish the river again. These rights were decided in a series of court decisions determining that the Klamath tribe’s water rights preceded those of farmers and municipalities, meaning that their rights to in-stream flows needed to be upheld. Numerous projects are underway to eliminate the dams on the Klamath River and return it to its original state.
Tribes with fishing rights in their treaties are now encroaching on the territories of tribes without such rights, leading to legal and political maneuvering between tribes. In Oregon, the Grand Ronde tribe was forced to purchase land at a key fishing location, Willamette Falls, and had to sidestep federal permissions, working with the state to gain “ceremonial” rights. Ultimately, the intertribal conflicts are caused by tribal adherence to federal bureaucratic processes that rely on legal or political channels to resolve problem rather than traditional tribal methods that bring people to the table to form agreements under traditional protocols.
Culture and Language
Native languages are the most threatened part of the cultures of Native peoples. Many tribes now have only a handful of people who fluently speak the tribe’s language. Of the estimated 10,000 languages once spoken worldwide, at least half have now gone extinct with no speakers, and there are 3,018 Indigenous languages spoken worldwide that are today endangered. One assessment of the 115 Indigenous languages currently spoken in the United State rates two as healthy, 34 as in danger, and 79 likely to go extinct within a generation (Nagle 2019). The rate and severity of language loss is connected to the remaining population of the tribe, whether the tribe has a functioning cultural center, and whether the language continues to be spoken in the households of tribal members. In large part, tribal people of the United States are becoming English-only speakers (Crawford 1995).
Language recovery and revitalization have become a focus of many Indigenous peoples. Many tribal members consider knowledge of their language to be the true determinant of tribal identity. Complex understandings of philosophies and lifeways are embedded in language. In addition, tribes believe that their ancestors’ spirits visit members of the tribe to speak with and advise them, and if a person does not know the language, they will not be able to understand them. Tribes are now working to restore, preserve, stabilize, and teach their languages to the next generations to preserve their knowledge and cultural identities. The University of California, Berkeley, developed a master-apprentice program that is helping many Indigenous groups develop more language speakers by partnering fluent speakers with young tribal members. Even with this type of training, it can take years to learn to fluently speak the language. Another approach is the language immersion program, inspired by Hawaiian and Maori educational models. The immersion model places students in immersive classrooms for a period of several years, in which only the Native language is spoken. Evening classes are also offered for adult learners.
In addition to efforts to restore Native languages, many tribes and urban tribal organizations offer cultural education classes to teach traditional skills. Art and craft classes are quite popular. Classes offered by Native instructors teach traditional techniques for making bows and arrows, weaving baskets, drawing in traditional styles, beading, and making moccasins, among others. History is another area that is receiving some attention. As just one example, the Cherokee Nation has instituted a history program for tribal members and tribal government staff so that all people working with and for the tribe have a shared understanding of history. Finally, Native events and celebrations typically draw substantial crowds. Many tribes and organizations host events such as powwows and tribal dances annually. These events are free to attend and present many different styles of dance and drum music, along with the opportunity to shop for Native arts and crafts. Powwows are usually multi-tribal events, in part reflecting the origin of these events in intertribal boarding schools.
Tribal cultures and languages are a deep part of Native identity. There was a time in the United States when Native people were heavily exposed to assimilation pressures. During this time, many Native people stopped identifying as Native and did not teach their language or culture to their children or grandchildren. Acceptance of Native peoples has now shifted in most regions of the United States, and Indigenous peoples do not experience as much overt racism as they have in the past, although there are still some areas in the United States—many on the borders of tribal reservations—where overt racism against Indigenous peoples persists (Ashley 2015). Many of the descendants of once reservation-bound tribes are now actively seeking to reassociate themselves with their tribal cultures, recognizing this part of their heritage as a central part of their identity.
Traditional Material Culture
The traditional material cultures of Indigenous peoples showcase an impressive array of styles and skills. Native art was heavily collected by individuals and museums in the 19th century, when there were fears that Indigenous cultures were disappearing. Native art remains popular today. While many Indigenous artists continue to work in traditional styles, some are also incorporating contemporary styles and techniques. Native material cultures embed much cultural philosophy. As anthropologist and museum director Nancy Parezo says, “To anthropologists, Native American/First Nation arts are windows to understanding other cultures and societies. They can be specimens used to support evolutionary theories or explain the maker’s cultural concepts of beauty—to show universal concepts and cultural differences, shared meanings, and modes of communication” (1990, 12).
Artistic styles such as petroglyphs , in which images are carved into stone, and pictographs , or drawings, can be appreciated as both historic and spiritual statements. The petroglyph site in Cascadia Cave, near Sweet Home, Oregon, has hundreds of carvings. The most easily recognizable are the bear paws on the wall of the cave. There are also numerous lines, zigzags, and holes carved out of the cave wall. Willamette Forest Service archaeologist Tony Farque noted that people had long thought that the place was used to gain “bear power” for Native shamans. However, when one steps back, it is apparent that the decorated area of the wall is bordered by a large relief of a salmon, with one hole as its eye and the carved lines creating gills. The cave is now understood as a site where Indigenous peoples—Kalapuya, Molala, and other tribes in the region—sought to gain power when fishing in the nearby South Fork Santiam River, where salmon were known to spawn.
Cultural sites such as Cascadia Cave are in danger of being destroyed by too much attention from archaeologists and the public. For more than a century, Cascadia Cave has been visited by thousands of tourists who have touched the walls, dug in the ground in search of artifacts, taken rubbings of the carvings, and sometimes even carved their initials or painted over petroglyphs to make them stand out more. All these activities degrade the site. Early archaeologists did much the same, digging into the ground and moving many yards of dirt, which has caused rainfall to pool at the walls of the cave. The pooling moisture accelerates the growth of mosses and other plants, which also degrade the walls of the cave. Digging also destroys the archaeological context of the site. It is important to note that in many countries, including the United States, it is illegal to dig up and remove archaeological materials. Those who continue to dig up materials for private collection or for sale are conducting illegal activities. Many of the sites illegally dug are cemetery sites, containing the remains of people and cultural artifacts that are related to descendant tribal populations today.
Weaving arts are another significant aspect of material culture for many Indigenous peoples. Basketry techniques were and still are used to construct vessels used for regular household and resource-gathering activities. Indigenous groups developed various techniques for weaving, such as right twist, left twist, overlay, and false embroidery. These techniques result in decorative styles unique to individual tribes. Weaving techniques make use of many natural materials. Large objects such as mats were typically made with cattail and tule, while baskets could be made from a wide variety of materials, including juncus, hazel branches, cedar bark, bear grass, spruce roots, willow, and maidenhair fern. Some materials were chosen for their stability and durability, others for their flexibility, and still others for their color and luster. Dyeing weaving materials created complex color variations. Baskets were even used for cooking. The technique for boiling water in a basket is similar across many cultures: the basket would be tightly woven, normally with a double weave, and then filled with water. The fibers of the basket and the tight weave created a watertight exterior; additionally, some traditions coated the fibers with grease or pitch. Hot rocks, heated in a fire, would be placed in the basket to make the contained liquid boil. In this manner, food could be cooked without destroying the basket.
Many tribes now offer classes to teach people the basic techniques and styles particular to their tribal heritage. The Confederated Tribes of Grand Ronde offer classes in carving, weaving arts, beading, regalia making, drum making, and other arts associated with the 27 tribes that make up the confederation. Arts and crafts are intermixed with education about Native philosophy, spirituality, and language. Some people attend classes for years to master the art style they enjoy, and tribal members may apprentice with master artisans to learn more advanced techniques. Many artisans are creating works of art that are inspired by deep feelings of Native identity, using their art to define themselves and their people within the contexts of both the present and the past. Several artists have become professionals and are producing work for galleries, exhibits, exterior monuments, and contracted sales. The artists employ traditional arts as well as contemporary sculptures and artistic traditions such as painting, drawing, and illustration. Many traditional three-dimensional artworks, such as cedar statues, are now rendered in metal, stone, or even glass so that they are more durable and can survive the rigors of contemporary tourism.
Indigenous Philosophy and Worldviews
A shared element of Indigenous philosophy across various cultures is the conception of humans existing in relationship to the world around them. Native peoples believe they are deeply connected to the natural world; animals are viewed as relatives, and plants, rocks, and mountains are all understood to have animistic spirits. Rivers, lakes, and even the seasons themselves are also understood as having spirits. Many Native American peoples believe that animals were once their brothers and sisters. It is believed that from the actions of some of the godlike animals, such as Coyote, Beaver, and Raven, much of the world was made. Many Native peoples gain shamanic powers by forming close relationships with certain animals. These powers might include the ability to heal, to poison, to call salmon, to call weather, to fish, or to communicate with animals. Typically, these abilities are gained through ceremonies designed to familiarize people with their spirit helpers at a young age. Ceremonies differ, but a common format involves a youth going off by themselves into a special natural area—such as a forest, hilltop, or mountain cave—and fasting and meditating until they hear their helper spirit. In this manner, many Native peoples are connected to spiritual powers; the most powerful may become a shaman or spiritual leader of their tribe. Details of these types of ceremonies are kept secret within each tribe. One reason for this secrecy is a concern that non-Native people might attempt the same ceremonies without guidance and perhaps hurt themselves or the world around them in the process.
Native philosophy is understood to be embodied in the elders of the tribes. By living a full life within their particular cultural context, tribal elders gain wisdom about their people and culture. Many maintain tribal languages, too. Elders are honored and supported by younger members of their societies, who in turn learn about tribal traditions and philosophies from the elders. Elders come to their position partly through age, but normally they are recognized by their tribes when they exhibit great wisdom. Certain elders may have greater status than others depending on how well versed they are in their traditions and how respected they are by the community.
Native philosophy can also be gleaned through the study of oral histories. Many oral histories relate to subjects such as how the world was formed, how humans relate to animals, and how to acquire food, offering moral and ethical lessons. Oral histories may also be records of historic events, such as when the tribe was removed to a reservation, when many people died from disease, when a tsunami forced the people to escape to a mountain, when the land was changed by geological activity, or when there was a war. Oral histories are often full of metaphors and symbols of powerful spiritual forces that caused the event. One example is the story told by the Wasco people of when Coyote and Wishpoosh (Beaver) fought on the Columbia River and created the Columbia Gorge. This oral history reflects Native explanations of a series of flood events that occurred when rushing floodwaters carved out the Columbia Gorge in Oregon. The Missoula floods occurred from 18,000 to 15,000 years ago during the large Ice Age. The floods, perhaps as many as 90 of them, are noted by geologists to have been caused by the breaking of glacial ice dams behind which was Lake Missoula. During fluctuations in the warming period, the ice dams burst, and millions of hectares of water from the glacial lake flooded down the Columbia to carve out the Columbia River Gorge. The dams would refreeze and burst again, perhaps hundreds of times, to scour the lands east of the Columbia of topsoil and carve out the gorge. The topsoil would be deposited in the Willamette Valley (Allen, Burns, and Burns 2009). It is remarkable that Native peoples maintained oral histories documenting this event for at least 15,000 years. The Wasco oral history of Wishpoosh and Coyote is only one such story of this event. All tribes in the region have a story that mentions a flood of this magnitude.
Indigenous worldviews are embedded in ceremonies as well. The Tolowa Nation of Northern California practices Nee-dash, their world renewal ceremony, also called the Feather Dance, on the winter and summer solstices. This ceremony lasts as long as 10 days and is meant to showcase the wealth of the tribe. Dancers, both men and women, wear regalia and dance continuously for the 10 days of the ceremony. Each day, they increase the number of necklaces they wear and the wealth displayed in their regalia. When the dancers become “wealthier,” it is a metaphor for the growth of food, understood as the wealth of the land, that begins in the spring of each year. Dancers move in a semicircle, men on one side and women on the other, as a leader sings Native ceremonial songs and stamps out a beat on the hard-packed earthen floor with a tall stamper stick. Dancers take turns “coming out” and dancing, individually or in twos, threes, or larger groups, understood to be displaying their ceremonial power in hunting, fishing, or gathering. An audience of tribal people is normally situated around the benches of the dance house, men on one side and women on the other. The dances are meant to renew the earth to ensure strong returns of seasonal fish runs, good hunting opportunities, and rich yields of acorns or berries. The ceremony honors the land, the animals, and the plants that sustain the people. This ceremony establishes a spiritual relationship in which people are not separate from nature but a part of it, with the responsibility to act as stewards of its great wealth.
Most Indigenous cultures have ceremonies similar to this, centered on events such as the first salmon catch, the first hunt, or the first gathering of any important food. First salmon ceremonies for the Takelma peoples of the Rogue River Valley in Oregon involve a young man taking the bones of the first salmon caught that year down to the bottom of the Rogue River. These ceremonies are an important way for Native peoples to acknowledge and recommit themselves to a responsibility to steward the natural world in order to sustain its health and vibrancy so that the people who rely on it may thrive into the future.
Indigenous Critique: Rights, Activism, Appropriation, and Stereotypes
In the contemporary era, the publications of academics have had a great deal of influence on how tribes have been treated by the federal government and other groups. A 1997 essay, titled “Anthropology and the Making of Chumash Tradition,” included the authors’ opinion that the Coast Chumash tribe were descendants of Mexican people, and not Native people of North America at all (Haley and Wilcoxon 1997). The essay relied in part on rumors that were later refuted as unproven by archaeologist Jon Erlandson (1998). These claims, even disproven, aided other Native peoples in accusing the Coast Chumash of not being Native, resulting in many social and political problems for the community. Scholarly publications such as these can affect the ability of tribal nations in the United States to gain federal recognition status because all applicants for federal recognition must establish continuous culture and governance. Public and scholarly opinions can have a huge effect on whether tribes get recognized and are able to restore their culture and sovereignty after centuries of colonization.
Responses to the disempowering effects of colonialism have sometimes been overtly political. In the 1960s, the American Indian Movement (AIM) took actions to bolster tribal sovereignty throughout the United States. AIM was involved with several highly public activities, including an occupation at Mount Rushmore in 1971 in protest over the illegal taking of Sioux lands and the carving of presidents’ faces in a mountain sacred to the Sioux. AIM also participated in the occupation of Wounded Knee in 1973, the site of a historic battleground, in protest over the failure to impeach Oglala Sioux president Richard Wilson; the resulting standoff with federal law enforcement lasted 71 days. Public awareness of the federal government’s oppression of Native peoples grew when a large military force was deployed during a second occupation of Wounded Knee, an event called Wounded Knee 2. AIM’s work was part of a larger civil rights movement that involved Black, Latina/Latino, and women activists as well as the growing anti–Vietnam War movement. This larger movement created political shifts in the United States that benefited Native communities (Johansen 2013).
Beginning in the 1970s, several laws were passed by Congress to empower tribes. These included policies pertaining to education (Indian Education Act, 1972), child foster care (Indian Child Welfare Act, 1978), college education (Tribally Controlled Colleges and Universities Assistance Act, 1978), freedom of religion (American Indian Religious Freedom Act, 1978), and rights to archaeological sites and remains (Archaeological Resources Protection Act, 1979, and Native American Graves and Repatriation Act, 1990). This period also saw the end of the national policy of termination and a turn toward allowing tribes that had been terminated to be restored, with self-determination becoming standard federal policy.
Stereotypes
Native peoples have also become vocal in confronting stereotypes about them. The first Western stereotypes of Native peoples in North American depicted them in primitivist terms as noble savages , living in harmony with nature, with no notions of laws, time, or money. Implicit in this view was the idea that Indigenous peoples were not fully civilized and did not deserve the same rights as White, Christian people. Their land could thus be taken away. This stereotype has been described by writer Albert Memmi “as a series of negations: they were not fully human, they were not civilized enough to have systems, they were not literate, their languages and modes of thought were inadequate” (Smith 2021, 31). Throughout the history of the United States, these stereotypes have been used to progressively take more and more away from Native peoples. When reservations were first established, they were said to be permanent homes, but as White settlers began to see these lands as attractive places, the notion was again raised that Native peoples were not using the land appropriately.
Additional stereotypes originated with early anthropological research. Notions that Native peoples could not digest alcohol, were lazy and would not work, were not intelligent enough to become civilized, or were dying off as a population because they did not have a civilized culture have all been perpetuated by scholars who embraced social evolutionary theories about human societies. The idea that societies and civilizations existed in competition with one another, and that Native peoples were not competitive because they were savages or barbarians, was inspired by Lewis Henry Morgan’s proposal of a hierarchy of civilizations. These ideas have been heavily refuted, but the stereotypes persist and continue to affect Native peoples in prejudicial ways.
Recently, the issue of Indian mascots has received a lot of attention. In the early 20th century, private and professional sports teams and franchises begin to name their athletic teams after Native groups or some characteristic words referring to Native peoples. Common names include the Warriors, Chiefs, Indians, Reds, Redskins, and Braves. Some of these names may have been chosen to honor the strength and resilience of people who had survived centuries of war with colonizing peoples. Regardless of the original intention, as time went on, fans of many of these teams developed practices that disparaged Indigenous peoples. Many mascots were cartoonish or savage caricatures. These mascots may have been the only exposure many American people had to Native peoples, at a time when there was no valid education about Native peoples offered in public schools.
The first significant challenge to the use of such mascots was led by Charlene Teters, a student at the University of Illinois, against the university’s mascot, Chief Illiniwek, in the 1980s. Teters criticized various aspects of the chief’s presentation, including the headdress, regalia, and dance style, the latter of which was the invention of students who took the role of mascot each year. The campaign against this mascot continued for some 20 years, with many fans and alumni of the university countering that the mascot was meant to honor the Illiniwek people. The mascot was finally dropped by the university in 2007.
Much opposition to mascots is connected not to the use of the figure itself but to the behavior of fans. Practices such as dressing in red paint, wearing outfits of fake feathers and fake headdresses, and using arm motions such as the “tomahawk chop” to show team spirit have offended Native groups. Names might also carry meanings not fully understood by fans. Controversy around the Washington Redskins’ name and mascot lasted for some 30 years. Many fans weren’t aware that the term redskins was used in states such as California and Oregon to refer to Native scalps collected by White American militia members. These scalps, or redskins, could be returned to the state government for a bounty. At certain periods in U.S. history, hundreds of Native people were killed, and whole villages sometimes destroyed, by militia seeking redskins to collect these bounties. In 2020, the Washington Redskins dropped the name, becoming known as the Washington Football Team until a replacement name was chosen. Similarly, in 2019, the Cleveland Indians dopped its “Chief Wahoo” mascot, and in 2021, the team changed its name to the Cleveland Guardians.
In some cases, tribal nations have collaborated with universities to develop more respectful mascot images. The University of Utah has collaborated with the Ute tribe in designing its mascot image featuring a feather, and Florida State University has worked with the Seminole tribe to develop its Appaloosa horse rider and spear imagery. There remains a political divide in the debate about mascots, with some Native activists believing there should be no Indian mascots, while others think that sovereign tribal nations, as sovereign governments, should be able to decide how their people are characterized by organized athletic organizations.


While working with other people’s copyrighted works, remember that their works are under copyright protection from the moment of creation.
Additionally, U.S. Copyright Law applies to works found on the Internet. Many of the works you find online are protected by copyright, even if there is no copyright notice. Your availability to access copyrighted materials on the Internet does not necessarily mean that you have the right to use, reuse and distribute the works in any manner you wish. It is important to respect copyright, whether the works are in a physical or digital format.
Risks of Infringing Copyright
If you violate one or more of the exclusive rights of a copyright owner, the copyright owner can bring a claim against you for copyright infringement. There are a few different penalties that are possible if you are accused of copyright infringement:
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Under specific circumstances, U.S. copyright law allows criminal prosecution in cases of willful infringement.
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If the infringing work is online, such as a video posted to YouTube, the copyright owner can request the material be taken down. This may be done through a Cease-and-Desist Letter or DMCA Takedown Notice. The material will be taken down and you will be notified of the accusation of infringement. If you believe that your use of the material is legal, you can respond with your explanation of why.
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The copyright owner can sue you. They could ask for an injunction to stop your use of their work. They can also ask for either actual damages or statutory damages. Actual damages are the actual amount of money the copyright owner lost due to your activity plus any profit you made from using the work. These can be hard to determine, so the law alternatively allows for statutory damages under certain conditions. These are a set range, from $750 to $30,000 per infringed work, that the judge or jury awards to the rights holder if you are found guilty. These damages can increase to $150,000 per infringed work if your use is determined to be a “willful” infringement.
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Some rights holders may offer the option of settling out of court. This agreed settlement may be cheaper than the cost of a trial for the rights holder and you.
The accusation of infringement is not the same as a conviction. You always have the right to defend your use.


2.6: Putting It Together- Summarizing Data Graphically and Numerically
Let’s Summarize
In Summarizing Data Graphically and Numerically , we focused on describing the distribution of a quantitative variable .
- To analyze the distribution of a quantitative variable, we describe the overall pattern of the data (shape, center, spread) and any deviations from the pattern (outliers). We use three types of graphs to analyze the distribution of a quantitative variable: dotplots, histograms, and boxplots.
- We described the shape of a distribution as left-skewed, right-skewed, symmetric with a central peak (bell-shaped), or uniform. Not all distributions have a simple shape that fits into one of these categories.
-
The
center
of a distribution is a typical value that represents the group. We have two different measurements for determining the center of a distribution: mean and median.
- The mean is the average. We calculate the mean by adding the data values and dividing by the number of individual data points. The mean is the fair share measure. The mean is also called the balancing point of a distribution. If we measure the distance between each data point and the mean, the distances are balanced on each side of the mean.
- The median is the physical center of the data when we make an ordered list. It has the same number of values above it as below it.
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General Guidelines for Choosing a Measure of Center
- Always plot the data. We need to use a graph to determine the shape of the distribution. By looking at the shape, we can determine which measure of center best describes the data.
- Use the mean as a measure of center only for distributions that are reasonably symmetric with a central peak. When outliers are present, the mean is not a good choice.
- Use the median as a measure of center for all other cases.
-
The
spread
of a distribution is a description of how the data varies. We studied three ways to measure spread:
range
(max – min), the
interquartile range
(Q3 – Q1), and the
standard deviation
. When we use the median, Q1 to Q3 gives a typical range of values associated with the middle 50% of the data. When we use the mean, Mean ± SD gives a typical range of values.
- The interquartile range (IQR) measures the variability in the middle half of the data.
- Standard deviation measures roughly the average distance of data from the mean.
- Outliers are data points that fall outside the overall pattern of the distribution. When using the median and IQR to measure center and spread, we use the 1.5 * IQR interval to identify outliers. Specifically, points outside the interval Q1 – 1.5 * IQR to Q3 + 1.5 * IQR are labeled as outliers.
Contributors and Attributions
CC licensed content, Shared previously
- Concepts in Statistics. Provided by : Open Learning Initiative. Located at : http://oli.cmu.edu . License : CC BY: Attribution


5.5: Gauss’ Law - Integral Form
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Gauss’ Law is one of the four fundamental laws of classical electromagnetics, collectively known as Maxwell’s Equations . Before diving in, the reader is strongly encouraged to review Section 2.4. In that section, Gauss’ Law emerges from the interpretation of the electric field as a flux density. Section 2.4 does not actually identify Gauss’ Law, but here it is:
Gauss’ Law (Equation \ref{m0014_eGL}) states that the flux of the electric field through a closed surface is equal to the enclosed charge.
Gauss’ Law is expressed mathematically as follows:
\[\boxed{ \oint_{\mathcal S} {\bf D}\cdot d{\bf s} = Q_{encl} } \label{m0014_eGL} \]
where \({\bf D}\) is the electric flux density \(\epsilon{\bf E}\), \({\mathcal S}\) is a closed surface with differential surface normal \(d{\bf s}\), and \(Q_{encl}\) is the enclosed charge. We can see the law is dimensionally correct; \({\bf D}\) has units of C/m\(^{2}\), thus integrating \({\bf D}\) over a surface gives a quantity with units of C/m\(^{2}\) \(\cdot\) m\(^{2}\) = C, which are the units of charge.
Gauss’ Law has a number of applications in electromagnetic theory. One of them, as explored below, is as a method to compute the electric field in response to a distribution of electric charge. Note that a method to do this, based on Coulomb’s Law, is described in Sections 5.1, 5.2, and 5.4. Gauss’ Law provides an alternative method that is easier or more useful in certain applications.
Example \(\PageIndex{1}\): Electric field associated with a charged particle, using Gauss’ Law.
In this example, we demonstrate the ability of Gauss’ Law to predict the field associated with a charge distribution. Let us do this for the simplest possible charge distribution. A particle of charge \(q\) located at the origin, for which we already have the answer (Section 5.1).
Solution
Gauss’ Law applies to any surface that encloses the charge, so for simplicity we chose a sphere of radius \(r\) centered at the origin. Note that \(Q_{encl}\) on the right hand side is just \(q\) for any surface having \(r>0\). Gauss’ Law in this case becomes
\[\int_{\theta=0}^{\pi} \int_{\phi=0}^{2\pi} { {\bf D} \cdot \left(\hat{\bf r}r^2 \sin\theta~d\theta~d\phi\right) } = q \nonumber \]
If we can solve for \({\bf D}\), we can get \({\bf E}\) using \({\bf D} = \epsilon {\bf E}\). The simplest way to solve for \({\bf D}\) is to use a symmetry argument, which proceeds as follows. In this problem, the magnitude of \({\bf D}\) can depend only on \(r\), and not \(\theta\) or \(\phi\). This is because the charge has no particular orientation, and the sphere is centered on the charge. Similarly, it is clear that \({\bf D}\) must point either directly toward or directly away from the charge. In other words, \({\bf D} = \hat{\bf r}D(r)\). Substituting this in the above equation, we encounter the dot product \(\hat{\bf r} \cdot \hat{\bf r}\), which is simply 1. Since \(D(r)\) and \(r^2\) are constants with respect to the integration, we obtain:
\[r^2 D(r) \int_{\theta=0}^{\pi} \int_{\phi=0}^{2\pi} { \sin\theta~d\theta d\phi } = q \nonumber \]
The remaining integral is simply \(4\pi\), thus we obtain: \[D(r) = \frac{q}{4\pi r^2} \nonumber \] Bringing the known vector orientation of \({\bf D}\) back into the equation, we obtain \[{\bf D} = \hat{\bf r}\frac{q}{4\pi r^2} \nonumber \] and finally using \({\bf D} = \epsilon {\bf E}\) we obtain the expected result \[{\bf E} = \hat{\bf r}\frac{q}{4\pi\epsilon r^2} \nonumber \]
Here’s the point you should take away from the above example:
Gauss’ Law combined with a symmetry argument may be sufficient to determine the electric field due to a charge distribution. Thus, Gauss’ Law may be an easier alternative to Coulomb’s Law in some applications.


29.4: Photon Momentum
Learning Objectives
By the end of this section, you will be able to:
- Relate the linear momentum of a photon to its energy or wavelength, and apply linear momentum conservation to simple processes involving the emission, absorption, or reflection of photons.
- Account qualitatively for the increase of photon wavelength that is observed, and explain the significance of the Compton wavelength.
Measuring Photon Momentum
The quantum of EM radiation we call a photon has properties analogous to those of particles we can see, such as grains of sand. A photon interacts as a unit in collisions or when absorbed, rather than as an extensive wave. Massive quanta, like electrons, also act like macroscopic particles—something we expect, because they are the smallest units of matter. Particles carry momentum as well as energy. Despite photons having no mass, there has long been evidence that EM radiation carries momentum. (Maxwell and others who studied EM waves predicted that they would carry momentum.) It is now a well-established fact that photons do have momentum. In fact, photon momentum is suggested by the photoelectric effect, where photons knock electrons out of a substance. Figure \(\PageIndex{1}\) shows macroscopic evidence of photon momentum.
Figure \(\PageIndex{1}\) shows a comet with two prominent tails. What most people do not know about the tails is that they always point away from the Sun rather than trailing behind the comet (like the tail of Bo Peep’s sheep). Comet tails are composed of gases and dust evaporated from the body of the comet and ionized gas. The dust particles recoil away from the Sun when photons scatter from them. Evidently, photons carry momentum in the direction of their motion (away from the Sun), and some of this momentum is transferred to dust particles in collisions. Gas atoms and molecules in the blue tail are most affected by other particles of radiation, such as protons and electrons emanating from the Sun, rather than by the momentum of photons.
Connections: Conservation of Momentum
Not only is momentum conserved in all realms of physics, but all types of particles are found to have momentum. We expect particles with mass to have momentum, but now we see that massless particles including photons also carry momentum.
Momentum is conserved in quantum mechanics just as it is in relativity and classical physics. Some of the earliest direct experimental evidence of this came from scattering of x-ray photons by electrons in substances, named Compton scattering after the American physicist Arthur H. Compton (1892–1962). Around 1923, Compton observed that x rays scattered from materials had a decreased energy and correctly analyzed this as being due to the scattering of photons from electrons. This phenomenon could be handled as a collision between two particles—a photon and an electron at rest in the material. Energy and momentum are conserved in the collision (Figure \(\PageIndex{2}\)) He won a Nobel Prize in 1929 for the discovery of this scattering, now called the Compton effect , because it helped prove that photon momentum is given by
\[p = \dfrac{h}{\lambda},\]
where \(h\) is Planck's constant and \(\lambda\) is the photon wavelength. (Note that relativistic momentum given as \(p = \gamma mu\) is valid only for particles having mass.)
We can see that photon momentum is small, since \(p = h/\lambda\) and \(h\) is very small. It is for this reason that we do not ordinarily observe photon momentum. Our mirrors do not recoil when light reflects from them (except perhaps in cartoons). Compton saw the effects of photon momentum because he was observing x rays, which have a small wavelength and a relatively large momentum, interacting with the lightest of particles, the electron.
Example \(\PageIndex{1}\): Electron and Photon Momentum Compared
- Calculate the momentum of a visible photon that has a wavelength of 500 nm.
- Find the velocity of an electron having the same momentum.
- What is the energy of the electron, and how does it compare with the energy of the photon?
Strategy
Finding the photon momentum is a straightforward application of its definition: \(p = \frac{h}{\lambda}\).
If we find the photon momentum is small, then we can assume that an electron with the same momentum will be nonrelativistic, making it easy to find its velocity and kinetic energy from the classical formulas.
Solution for (a)
Photon momentum is given by the equation: \[p = \dfrac{h}{\lambda}. \nonumber\]
Entering the given photon wavelength yields
\[p = \dfrac{6.63 \times 10^{-34} \, J \cdot s}{500 \times 10^{-0} \, m} = 1.33 \times 10^{-27} \, kg \cdot m/s. \nonumber\]
Solution for (b)
Since this momentum is indeed small, we will use the classical expression \(p = mv\) to find the velocity of an electron with this momentum. Solving for \(v\) and using the known value for the mass of an electron gives
\[v = \dfrac{p}{m} = \dfrac{1.33 \times 10^{-27} \, kg \cdot m/s}{9.11 \times 10^{-31} \, kg} = 1460 \, m/s \approx 1460 \, m/s. \nonumber\]
Solution for (c)
The electron has kinetic energy, which is classically given by
\[KE_e = \dfrac{1}{2} mv^2. \nonumber\]
Thus,
\[KE_e = \dfrac{1}{2} (9.11 \times 10^{-31} \, kg)(1455 \, m/s)^2 = 9.64 \times 10^{-25} \, J. \nonumber\]
Converting this to eV by multiplying by \((1 \, eV)/(1.602 \times 10^{-19} \, J)\) yields
\[KE_e = 6.02 \times 10^{-6} \, eV. \nonumber\]
The photon energy \(E\) is
\[E = \dfrac{hc}{\lambda} = \dfrac{1240 \, eV \cdot nm}{500 \, nm} = 2.48 \, eV, \nonumber\]
which is about five orders of magnitude greater.
Discussion
Photon momentum is indeed small. Even if we have huge numbers of them, the total momentum they carry is small. An electron with the same momentum has a 1460 m/s velocity, which is clearly nonrelativistic. A more massive particle with the same momentum would have an even smaller velocity. This is borne out by the fact that it takes far less energy to give an electron the same momentum as a photon. But on a quantum-mechanical scale, especially for high-energy photons interacting with small masses, photon momentum is significant. Even on a large scale, photon momentum can have an effect if there are enough of them and if there is nothing to prevent the slow recoil of matter. Comet tails are one example, but there are also proposals to build space sails that use huge low-mass mirrors (made of aluminized Mylar) to reflect sunlight. In the vacuum of space, the mirrors would gradually recoil and could actually take spacecraft from place to place in the solar system (Figure \(\PageIndex{3}\)).
Relativistic Photon Momentum
There is a relationship between photon momentum \(p\) and photon energy \(E\) that is consistent with the relation given previously for the relativistic total energy of a particle as
\[E^2 = (pc)^2 + (mc^2)^2. \label{photon1}\]
We know \(m\) is zero for a photon, but \(p\) is not, so that Equation \ref{photon1} becomes
\[E = pc,\] or \[p = \dfrac{E}{c} \text{(for photons)}. \nonumber\]
To check the validity of this relation, note that \(E = hc/\lambda\) for a photon. Substituting this into \(p = E/c\) yields
\[p = (hc/\lambda) / c = \dfrac{h}{\lambda},\]
as determined experimentally and discussed above. Thus, \(p = E/c\) is equivalent to Compton’s result \(p = h/\lambda.\) For a further verification of the relationship between photon energy and momentum, see Example \(\PageIndex{3}\).
Photon Detectors
Almost all detection systems talked about thus far—eyes, photographic plates, photomultiplier tubes in microscopes, and CCD cameras—rely on particle-like properties of photons interacting with a sensitive area. A change is caused and either the change is cascaded or zillions of points are recorded to form an image we detect. These detectors are used in biomedical imaging systems, and there is ongoing research into improving the efficiency of receiving photons, particularly by cooling detection systems and reducing thermal effects.
Example \(\PageIndex{2}\): Photon Energy and Momentum
Show that \(p = E/c\) for the photon considered in the Example \(\PageIndex{2}\) .
Strategy
We will take the energy \(E\) found in Example \(\PageIndex{2}\) , divide it by the speed of light, and see if the same momentum is obtained as before.
Solution
Given that the energy of the photon is 2.48 eV and converting this to joules, we get
\[p = \dfrac{E}{c} = \dfrac{(2.48 \, eV)(1.60 \times 10^{-19} \, J/eV)}{3.00 \times 10^8 \, m/s} = 1.33 \times 10^{-27} \, kg. \nonumber\]
Discussion
This value for momentum is the same as found before (note that unrounded values are used in all calculations to avoid even small rounding errors), an expected verification of the relationship \(p = E/c\). This also means the relationship between energy, momentum, and mass given by \(E^2 = (pc)^2 + (mc)^2 \) applies to both matter and photons. Once again, note that \(p\) is not zero, even when \(m\) is.
PROBLEM-SOLVING SUGGESTIONS
Note that the forms of the constants \(h = 4.14 \times 10^{-15} \, eV \cdot s\) and \(hc = 1240 \, eV \cdot nm\) may be particularly useful for this section’s Problems and Exercises.
Summary
- Photons have momentum, given by \(p = \frac{h}{\lambda}\), where \(\lambda\) is the photon wavelength.
- Photon energy and momentum are related by \(p = \frac{E}{c}\), where \(E = hf = hc/\lambda\) for a photon.
Glossary
- photon momentum
- the amount of momentum a photon has, calculated by \(p = \frac{h}{\lambda} = \frac{E}{c}\)
- Compton effect
- the phenomenon whereby x rays scattered from materials have decreased energy


8.1.4: Categories and Concepts
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The information we sense and perceive is continuously organized and reorganized into concepts that belong to categories . Most concepts cannot be strictly defined but are organized around the best examples or prototypes, which have the properties most common in the category or might be considered the ideal example of a category.
Concepts are at the core of intelligent behavior. We expect people to be able to know what to do in new situations and when confronting new objects. If you go into a new classroom and see chairs, a blackboard, a projector, and a screen, you know what these things are and how they will be used. You’ll sit on one of the chairs and expect the instructor to write on the blackboard or project something onto the screen. You’ll do this even if you have never seen any of these particular objects before, because you have concepts of classrooms, chairs, projectors, and so forth that tell you what they are and what you’re supposed to do with them.
Objects fall into many different categories, but there is usually a hierarchy to help us organize our mental representations.
- A concept at the superordinate level of categories is at the top of a taxonomy and it has a high degree of generality (e.g., animal, fruit).
- A concept at the basic level categories is found at the generic level which contains the most salient differences (e.g., dog, apple).
- A concept at the subordinate level of categories is specific degree and has little generality (e.g., Labrador retriever, Gala).
Brown (1958) noted that children use basic level categories when first learning language and superordinates are especially difficult for children to fully acquire. People are faster at identifying objects as members of basic-level categories (Rosch et al., 1976). Recent research suggests that there are different ways to learn and represent concepts and that they are accomplished by different neural systems. Using our earlier example of classroom, if someone tells you a new fact about the projector, like it uses a halogen bulb, you are likely to extend this fact to other projectors you encounter. In short, concepts allow you to extend what you have learned about a limited number of objects to a potentially infinite set of events and possibilities.
Categorization and Culture
There are some universal categories like emotions, facial expressions, shape and color but culture can shape how we organize information. Chiu (1972) was the first to examine cultural differences in categorization using Chinese and American children. Participants were presented with three pictures (e.g., a tire, a car, and a bus), and were asked to group the two pictures they thought best belonged together. Participants were also asked to explain their choices (e.g., “Because they are both large”). Results showed that the Chinese children have a greater tendency to categorize by identifying relationships among the pictures but American children were more likely to categorize by identifying similarities among pictures.
Later research reported no cultural differences in categorization between Western and East Asian participants; however, among similarity categorizations the East Asian participants were more likely to make decisions on holistic aspects of the images and Western participants were more like to make decisions based on individual components of the images (Norenzayan, Smith, Jun Kim, and Nisbett, 2002). Cultural differences in categorizing were also found by Unworth, Sears and Pexman (2005) across three experiments however, when the experiment task was timed there were differences in category selection. These results suggest that the nature (timed or untimed) of the categorization task determines the extent to which cultural differences are observed.
The results of these categorization studies seem to support the differences in thinking between individualist and collectivist cultures. Western cultures are more individualist and engage in more analytic thinking and East Asian cultures engage in more holistic thinking (Choi, Nisbett, & Smith, 1997; Masuda & Nisbett, 2001; Nisbett et al., 2001; Peng & Nisbett, 1999). You might remember from the earlier section that holistic thought is characterized by a focus on context and environmental factors so categorizing by relationships can be explained with referencing how objects relate to their environment. Analytic thought is characterized by the separation of an object from its context so categorizing by similarity means that objects can be separated into different groups. A major limitation with these studies is the emphasis on East Asian, specifically the use of Chinese participants and Western cultures. There have been no within culture replications using participants from other non-Asian collectivist cultures.


30.24: Plant Defense Mechanisms - Against Herbivores
- Identify plant defense responses to herbivores
Defense Responses Against Herbivores
Herbivores, both large and small, use plants as food and actively chew them. Plants have developed a variety of strategies to discourage or kill attackers.
Mechanical Defenses
The first line of defense in plants is an intact and impenetrable barrier composed of bark and a waxy cuticle. Both protect plants against herbivores. Other adaptations against herbivores include hard shells, thorns (modified branches), and spines (modified leaves). They discourage animals by causing physical damage or by inducing rashes and allergic reactions. Some Acacia tree species have developed mutualistic relationships with ant colonies: they offer the ants shelter in their hollow thorns in exchange for the ants’ defense of the tree’s leaves.
Chemical Defenses
A plant’s exterior protection can be compromised by mechanical damage, which may provide an entry point for pathogens. If the first line of defense is breached, the plant must resort to a different set of defense mechanisms, such as toxins and enzymes. Secondary metabolites are compounds that are not directly derived from photosynthesis and are not necessary for respiration or plant growth and development.
Many metabolites are toxic and can even be lethal to animals that ingest them. Some metabolites are alkaloids, which discourage predators with noxious odors (such as the volatile oils of mint and sage) or repellent tastes (like the bitterness of quinine). Other alkaloids affect herbivores by causing either excessive stimulation (caffeine is one example) or the lethargy associated with opioids. Some compounds become toxic after ingestion; for instance, glycol cyanide in the cassava root releases cyanide only upon ingestion by the herbivore. Foxgloves produce several deadly chemicals, namely cardiac and steroidal glycosides. Ingestion can cause nausea, vomiting, hallucinations, convulsions, or death.
Timing
Mechanical wounding and predator attacks activate defense and protective mechanisms in the damaged tissue and elicit long-distancing signaling or activation of defense and protective mechanisms at sites farther from the injury location. Some defense reactions occur within minutes, while others may take several hours. In addition, long-distance signaling elicits a systemic response aimed at deterring predators. As tissue is damaged, jasmonates may promote the synthesis of compounds that are toxic to predators. Jasmonates also elicit the synthesis of volatile compounds that attract parasitoids: insects that spend their developing stages in or on another insect, eventually killing their host. The plant may activate abscission of injured tissue if it is damaged beyond repair.
Key Points
- Many plants have impenetrable barriers, such as bark and waxy cuticles, or adaptations, such as thorns and spines, to protect them from herbivores.
- If herbivores breach a plant’s barriers, the plant can respond with secondary metabolites, which are often toxic compounds, such as glycol cyanide, that may harm the herbivore.
- When attacked by a predator, damaged plant tissue releases jasmonate hormones that promote the release of volatile compounds, attracting parasitoids, which use, and eventually kill, the predators as host insects.