13: Galaxies
Today, we know that our Sun is just one of the many billions of stars that make up the huge cosmic island we call the Milky Way Galaxy. How can we “weigh” such an enormous system of stars and measure its total mass?
One of the most striking features you can see in a truly dark sky—one without light pollution—is the band of faint white light called the Milky Way, which stretches from one horizon to the other. The name comes from an ancient Greek legend that compared its faint white splash of light to a stream of spilled milk. But folktales differ from culture to culture: one East African tribe thought of the hazy band as the smoke of ancient campfires, several Native American stories tell of a path across the sky traveled by sacred animals, and in Siberia, the diffuse arc was known as the seam of the tent of the sky.
In 1610, Galileo made the first telescopic survey of the Milky Way and discovered that it is composed of a multitude of individual stars. Today, we know that the Milky Way comprises our view inward of the huge cosmic pinwheel that we call the Milky Way Galaxy and that is our home. Moreover, our Galaxy is now recognized as just one galaxy among many billions of other galaxies in the cosmos.
-
- 13.1: The Architecture of the Galaxy
- The Milky Way Galaxy consists of a thin disk containing dust, gas, and young and old stars; a spherical halo containing populations of very old stars, and globular star clusters; a thick, more diffuse disk with stars that have properties intermediate between those in the thin disk and the halo; a peanut-shaped nuclear bulge of mostly old stars around the center; and a supermassive black hole at the very center. The Sun is located roughly halfway out of the Milky Way.
-
- 13.2: Spiral Structure
- The gaseous distribution in the Galaxy’s disk has two main spiral arms that emerge from the ends of the central bar, along with several fainter arms and short spurs; the Sun is located in one of those spurs. Measurements show that the Galaxy does not rotate as a solid body, but instead its stars and gas follow differential rotation, such that the material closer to the galactic center completes its orbit more quickly.
-
- 13.3: The Mass of the Galaxy
- The Sun revolves completely around the galactic center in about 225 million years (a galactic year). The mass of the Galaxy can be determined by measuring the orbital velocities of stars and interstellar matter. The total mass of the Galaxy is about 2 × 10^12 \(M_{\text{Sun}}\). As much as 95% of this mass consists of dark matter that emits no electromagnetic radiation and can be detected only because of the gravitational force it exerts on visible stars and interstellar matter.
-
- 13.4: The Center of the Galaxy
- A supermassive black hole is located at the center of the Galaxy. Measurements of the velocities of stars located within a few light-days of the center show that the mass inside their orbits around the center is about 4.6 million \(M_{\text{Sun}}\). Radio observations show that this mass is concentrated in a volume with a diameter similar to that of Mercury’s orbit. The density of this matter concentration exceeds that of the densest known star clusters by a factor of nearly a million.
-
- 13.5: Stellar Populations in the Galaxy
- We can roughly divide the stars in the Galaxy into two categories. Old stars with few heavy elements are referred to as population II stars and are found in the halo and in globular clusters. Population I stars contain more heavy elements than globular cluster and halo stars, are typically younger and found in the disk, and are especially concentrated in the spiral arms. The Sun is a member of population I.
-
- 13.6: The Formation of the Galaxy
- The Galaxy began forming a little more than 13 billion years ago. Models suggest that the stars in the halo and globular clusters formed first, while the Galaxy was spherical. The gas, somewhat enriched in heavy elements by the first generation of stars, then collapsed from a spherical distribution to a rotating disk-shaped distribution. Stars are still forming today from the gas and dust that remain in the disk. Star formation occurs most rapidly in the spiral arms.
-
- 13.7: The Discovery of Galaxies
- Faint star clusters, clouds of glowing gas, and galaxies all appeared as faint patches of light (or nebulae) in the telescopes available at the beginning of the twentieth century. It was only when Hubble measured the distance to the Andromeda galaxy using cepheid variables with the giant 2.5-meter reflector on Mount Wilson in 1924 that the existence of other galaxies similar to the Milky Way in size and content was established.
-
- 13.8: Types of Galaxies
- Most bright galaxies are either spirals or ellipticals. Spiral galaxies contain both old and young stars, as well as interstellar matter, and have typical masses in the range of 10^9 to 10^12 \(M_{\text{Sun}}\). Ellipticals are spheroidal or slightly elongated systems that consist almost entirely of old stars, with very little interstellar matter. Elliptical galaxies range in size from giants, more massive than any spiral, down to dwarfs, with masses of only about 10^6 \(M_{\text{Sun}}\).
-
- 13.9: Properties of Galaxies
- The masses of spiral galaxies are determined from measurements of their rates of rotation. The masses of elliptical galaxies are estimated from analyses of the motions of the stars within them. Galaxies can be characterized by their mass-to-light ratios. The luminous parts of galaxies with active star formation typically have mass-to-light ratios in the range of 1 to 10; the luminous parts of elliptical galaxies typically have mass-to-light ratios of 10 to 20.
-
- 13.10: The Extragalactic Distance Scale
- Astronomers determine the distances to galaxies using a variety of methods, including the period-luminosity relationship for cepheid variables; objects such as type Ia supernovae, which appear to be standard bulbs; and the Tully-Fisher relation, which connects the line broadening of 21-cm radiation to the luminosity of spiral galaxies. Each method has limitations in terms of its precision, the kinds of galaxies with which it can be used, and the range of distances over which it can be applied.
-
- 13.11: The Expanding Universe
- The universe is expanding. Observations show that the spectral lines of distant galaxies are redshifted, and that their recession velocities are proportional to their distances from us, a relationship known as Hubble’s law. The rate of recession, called the Hubble constant, is approximately 22 kilometers per second per million light-years. We are not at the center of this expansion: an observer in any other galaxy would see the same pattern of expansion that we do.
-
- 13.12: Quasars
- The first quasars discovered looked like stars but had strong radio emission. Their visible-light spectra at first seemed confusing, but then astronomers realized that they had much larger redshifts than stars. The quasar spectra obtained so far show redshifts ranging from 15% to more than 96% the speed of light. Observations with the Hubble Space Telescope show that quasars lie at the centers of galaxies and that both spirals and ellipticals can harbor quasars.
-
- 13.13: Supermassive Black Holes- What Quasars really are
- Both active galactic nuclei and quasars derive their energy from material falling toward, and forming a hot accretion disk around, a massive black hole. This model can account for the large amount of energy emitted and for the fact that the energy is produced in a relatively small volume of space. It can also explain why jets coming from these objects are seen in two directions: those directions are perpendicular to the accretion disk.
-
- 13.14: Quasars as Probes of Evolution in the Universe
- Quasars and galaxies affect each other: the galaxy supplies fuel to the black hole, and the quasar heats and disrupts the gas clouds in the galaxy. The balance between these two processes probably helps explain why the black hole seems always to be about 1/200 the mass of the spherical bulge of stars that surrounds the black hole. Quasars were much more common billions of years ago than they are now, and astronomers speculate that they mark an early stage in the formation of galaxies.
-
- 13.15: Observations of Distant Galaxies
- When we look at distant galaxies, we are looking back in time. We have now seen galaxies as they were when the universe was about 500 million years old—only about five percent as old as it is now. The universe now is 13.8 billion years old. The color of a galaxy is an indicator of the age of the stars that populate it. Blue galaxies must contain a lot of hot, massive, young stars. Galaxies that contain only old stars tend to be yellowish red.
-
- 13.16: Galaxy Mergers and Active Galactic Nuclei
- When galaxies of comparable size collide and coalesce we call it a merger, but when a small galaxy is swallowed by a much larger one, we use the term galactic cannibalism. Collisions play an important role in the evolution of galaxies. If the collision involves at least one galaxy rich in interstellar matter, the resulting compression of the gas will result in a burst of star formation, leading to a starburst galaxy. Mergers were much more common when the universe was young.
-
- 13.17: The Distribution of Galaxies in Space
- Counts of galaxies in various directions establish that the universe on the large scale is homogeneous and isotropic (the same everywhere and the same in all directions, apart from evolutionary changes with time). The sameness of the universe everywhere is referred to as the cosmological principle. Galaxies are grouped together in clusters. The Milky Way Galaxy is a member of the Local Group, which contains at least 54 member galaxies.
-
- 13.18: The Challenge of Dark Matter
- Stars move much faster in their orbits around the centers of galaxies, and galaxies around centers of galaxy clusters, than they should according to the gravity of all the luminous matter (stars, gas, and dust) astronomers can detect. This discrepancy implies that galaxies and galaxy clusters are dominated by dark matter rather than normal luminous matter. Gravitational lensing and X-ray radiation from massive galaxy clusters confirm the presence of dark matter.
-
- 13.19: The Formation and Evolution of Galaxies and Structure in the Universe
- Initially, luminous and dark matter in the universe was distributed almost—but not quite—uniformly. The challenge for galaxy formation theories is to show how this “not quite” smooth distribution of matter developed the structures—galaxies and galaxy clusters—that we see today. It is likely that the filamentary distribution of galaxies and voids was built in near the beginning, before stars and galaxies began to form.
Thumbnail: T he Milky Way rises over Square Tower, an ancestral pueblo building at Hovenweep National Monument in Utah. Many stars and dark clouds of dust combine to make a spectacular celestial sight of our home Galaxy. The location has been designated an International Dark Sky Park by the International Dark Sky Association.
Contributors and Attributions
-
Andrew Fraknoi (Foothill College), David Morrison (NASA Ames Research Center), Sidney C. Wolff (National Optical Astronomy Observatory) with many contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at https://openstax.org/details/books/astronomy ).


3.2: Training Program
While employee orientation involves organizational information and expectations, employee training focuses on the acquisition of specific knowledge, skills, and attitudes. All new hires are not created equal, and a good training program can even out the differences significantly.
The problems that can potentially arise from lack of training, or from poor training, are numerous and serious:
- Low productivity
- Mistakes (often costly)
- Poor morale
- Employee grievances
- High waste
- Customer complaints
- Lost revenue
Properly trained employees deliver better service, are usually happier in their jobs, and are more motivated to accept new challenges and information (because they don’t feel overwhelmed).
Not only is training great for business, it’s also great for employees and employers —everyone is happier and more productive. As with most management concepts, training is most effective when it’s approached holistically and as a process—a series of steps designed to improve employee performance. Training should not be viewed as a cost either in time or money: it is one of the most important investments business managers can make because it dramatically increases the value of your key asset—your staff.
Understand the training process
The following steps outline a model training process:
- Review the job description and set training objectives.
- Select the trainees.
- Create a training plan.
- Determine the training methods and mode.
- Identify competent trainers.
- Choose a means of evaluating if your training was successful.
- Deliver the training.
- Evaluate the training.
It is important to document the training upon completion and to place notes in each employee’s file including what topics where covered, when, where, and how the employee was trained. You might also include the employee’s own evaluation of the training (if not anonymous or confidential) or other document demonstrating what the employee learned.
Use excellent trainers
Who actually conducts the training depends on the type of training needed and who will receive it. On-the-job training is typically conducted by supervisors or senior staff members. Off-the-job training can be conducted either by in-house personnel or outside instructors.
In-house training is the daily responsibility of supervisors and senior employees. Supervisors are ultimately responsible for the productivity and, therefore, the training of their subordinates. These supervisors should be taught the techniques of good training. They must be aware of the knowledge and skills necessary to make a productive employee. This information can be found in both the job analysis and the job description.
Trainers should be taught to establish goals and objectives for their training and to determine how these objectives can be used to influence the productivity of their departments. They also must be aware of how adults learn and how best to communicate with adults. Small businesses may need to develop their supervisors’ training capabilities by sending them to courses on training methods. The investment will pay off in increased productivity.
Train to the job description
Employee training isn’t always straightforward, particularly from the perspective of the employee. Employees don’t always make the connection between training and improved job performance. Using a job description as a base for training programs highlights the focus on job performance and ensures relevant training content.
Use employee training manuals
Most personnel problems are actually created by systems, procedures, and/or training problems. When job descriptions, procedure manuals, and adequate training are in place, many issues disappear.
As noted in previous sections, it all starts with planning, job analysis, and job descriptions for every employee. Comprehensive job descriptions break down duties, roles, and responsibilities into logical tasks. With those in place, you can then determine how to impart necessary information and instructions for each task employees need to master. Training manuals serve double duty as checklists for performance evaluations.


10.9.6: Chapter Test
Find \(\overleftrightarrow {AD} \cap \overline {CD}\).
Find \({\overline {AB}} \cup {\overline {BC}}\).
Use the given figure to find the angle measurements.
Given that \({l_1}\) and \({l_2}\) are parallel lines, solve the angle measurements for all the angles in the given figure.
Find the angle measurements in the given figure.
The two triangles shown are congruent by what theorem?
Find the sum of the interior angles of a regular heptagon.
Determine the scaling factor between these two similar triangles.
Find the measure of the missing angles in the figure shown.
Calculate the perimeter of a regular octagon with a side length of 5 cm.
Find the measurement of an interior angle of a regular heptagon.
Find the sum of the interior angles of a regular pentagon.
Find the measure of an exterior angle of a regular pentagon.
Find the circumference of the circle with a radius of 3.5 cm.
What are the four transformations that are used to produce tessellations?
Find the surface area of the triangular prism shown.
Find the volume of the right cylinder in the given figure.
Find the missing length in the given figure.
Find the missing length in the given figure.
Find the length of side \(b\) in the given figure.
Find the length of side \(a\) in the given figure.
Find the measure of \(\theta\) in the given figure.


1.5: Chemical Control of Microbial Growth
In this lab you will:
- Learn about disinfectants and the various factors that need to be considered when choosing a disinfectant.
- Set up an experiment to determine the effectiveness of five different common disinfectants
Introduction
The use of chemicals to control microbial growth dates back at least as far as the 1800’s. Tincture of iodine was used as antiseptic during the Civil War, and Joseph Lister established the practice of aseptic surgery using a disinfectant known as carbolic acid (phenol) in the 1860’s. Since that time, many types of disinfectants (agents that are used to eliminate or kill vegetative cells on surfaces) and antiseptics (agents that are used to eliminate or reduce vegetative cells on living tissue) have been used. Although disinfectants and antiseptics may be effective at killing vegetative cells, they do not usually achieve sterilization.
Various factors need to be considered when choosing a disinfectant or antiseptic. It is very important to know which microbes are present to determine what type of disinfectant would work best. It is also important to realize that the effectiveness of a particular disinfectant may be affected by pH, temperature, concentration , and exposure time. Ideal disinfectants should be effective against the particular contaminants present, usable at a low concentration, require a relatively short exposure time, and have a long shelf life. It should also be water soluble, non-toxic to humans and animals, and cost-effective.
Method
- Divide your plate into 10 sections as shown.

- Gently touch each finger to each of the 5 spaces to the left on the plate.
- One by one, wash each finger with a different chemical and imprint again on the right side of the place. Include your name, finger number, date, and chemical used.
- Bacterial growth will be observed next lab period.


1.E: Electronic Structure of Atoms (Exercises)
The Wave Nature of Light
Conceptual Problems
- What are the characteristics of a wave? What is the relationship between electromagnetic radiation and wave energy?
- At constant wavelength, what effect does increasing the frequency of a wave have on its speed? its amplitude?
- List the following forms of electromagnetic radiation in order of increasing wavelength: x-rays, radio waves, infrared waves, microwaves, ultraviolet waves, visible waves, and gamma rays. List them in order of increasing frequency. Which has the highest energy?
- A large industry is centered on developing skin-care products, such as suntan lotions and cosmetics, that cannot be penetrated by ultraviolet radiation. How does the wavelength of visible light compare with the wavelength of ultraviolet light? How does the energy of visible light compare with the energy of ultraviolet light? Why is this industry focused on blocking ultraviolet light rather than visible light?
Numerical Problems
-
The human eye is sensitive to what fraction of the electromagnetic spectrum, assuming a typical spectral range of 10 4 to 10 20 Hz? If we came from the planet Krypton and had x-ray vision (i.e., if our eyes were sensitive to x-rays in addition to visible light), how would this fraction be changed?
-
What is the frequency in megahertz corresponding to each wavelength?
- 755 m
- 6.73 nm
- 1.77 × 10 3 km
- 9.88 Å
- 3.7 × 10 −10 m
-
What is the frequency in megahertz corresponding to each wavelength?
- 5.8 × 10 −7 m
- 2.3 Å
- 8.6 × 10 7 m
- 6.2 mm
- 3.7 nm
-
Line spectra are also observed for molecular species. Given the following characteristic wavelengths for each species, identify the spectral region (ultraviolet, visible, etc.) in which the following line spectra will occur. Given 1.00 mol of each compound and the wavelength of absorbed or emitted light, how much energy does this correspond to?
- NH 3 , 1.0 × 10 −2 m
- CH 3 CH 2 OH, 9.0 μm
- Mo atom, 7.1 Å
-
What is the speed of a wave in meters per second that has a wavelength of 1250 m and a frequency of 2.36 × 10 5 s −1 ?
-
A wave travels at 3.70 m/s with a frequency of 4.599 × 10 7 Hz and an amplitude of 1.0 m. What is its wavelength in nanometers?
-
An AM radio station broadcasts with a wavelength of 248.0 m. What is the broadcast frequency of the station in kilohertz? An AM station has a broadcast range of 92.6 MHz. What is the corresponding wavelength range in meters for this reception?
-
An FM radio station broadcasts with a wavelength of 3.21 m. What is the broadcast frequency of the station in megahertz? An FM radio typically has a broadcast range of 82–112 MHz. What is the corresponding wavelength range in meters for this reception?
-
A microwave oven operates at a frequency of approximately 2450 MHz. What is the corresponding wavelength? Water, with its polar molecules, absorbs electromagnetic radiation primarily in the infrared portion of the spectrum. Given this fact, why are microwave ovens used for cooking food?
Quantized Energy and Photons
Conceptual Problems
- Describe the relationship between the energy of a photon and its frequency.
- How was the ultraviolet catastrophe explained?
- If electromagnetic radiation with a continuous range of frequencies above the threshold frequency of a metal is allowed to strike a metal surface, is the kinetic energy of the ejected electrons continuous or quantized? Explain your answer.
- The vibrational energy of a plucked guitar string is said to be quantized. What do we mean by this? Are the sounds emitted from the 88 keys on a piano also quantized?
- Which of the following exhibit quantized behavior: a human voice, the speed of a car, a harp, the colors of light, automobile tire sizes, waves from a speedboat?
Conceptual Answers
-
The energy of a photon is directly proportional to the frequency of the electromagnetic radiation.

Numerical Problems
-
What is the energy of a photon of light with each wavelength? To which region of the electromagnetic spectrum does each wavelength belong?
- 4.33 × 10 5 m
- 0.065 nm
- 786 pm
-
How much energy is contained in each of the following? To which region of the electromagnetic spectrum does each wavelength belong?
- 250 photons with a wavelength of 3.0 m
- 4.2 × 10 6 photons with a wavelength of 92 μm
- 1.78 × 10 22 photons with a wavelength of 2.1 Å
-
A 6.023 x 10 23 photons are found to have an energy of 225 kJ. What is the wavelength of the radiation?
-
Use the data in Table 2.1.1 to calculate how much more energetic a single gamma-ray photon is than a radio-wave photon. How many photons from a radio source operating at a frequency of 8 × 10 5 Hz would be required to provide the same amount of energy as a single gamma-ray photon with a frequency of 3 × 10 19 Hz?
-
Use the data in Table 2.1.1 to calculate how much more energetic a single x-ray photon is than a photon of ultraviolet light.
-
A radio station has a transmitter that broadcasts at a frequency of 100.7 MHz with a power output of 50 kW. Given that 1 W = 1 J/s, how many photons are emitted by the transmitter each second?
Numerical Answers
-
- 4.59 × 10 −31 J/photon, radio
- 3.1 × 10 −15 J/photon, gamma ray
- 2.53 × 10 −16 J/photon, gamma ray
-
-
532 nm
Line Spectra and the Bohr Model
Conceptual Problems
-
Is the spectrum of the light emitted by isolated atoms of an element discrete or continuous? How do these spectra differ from those obtained by heating a bulk sample of a solid element? Explain your answers.
-
Explain why each element has a characteristic emission and absorption spectra. If spectral emissions had been found to be continuous rather than discrete, what would have been the implications for Bohr’s model of the atom?
-
Explain the differences between a ground state and an excited state. Describe what happens in the spectrum of a species when an electron moves from a ground state to an excited state. What happens in the spectrum when the electron falls from an excited state to a ground state?
-
What phenomenon causes a neon sign to have a characteristic color? If the emission spectrum of an element is constant, why do some neon signs have more than one color?
-
How is light from a laser different from the light emitted by a light source such as a light bulb? Describe how a laser produces light.
Numerical Problems
-
Using a Bohr model and the transition from n = 2 to n = 3 in an atom with a single electron, describe the mathematical relationship between an emission spectrum and an absorption spectrum. What is the energy of this transition? What does the sign of the energy value represent in this case? What range of light is associated with this transition?
-
If a hydrogen atom is excited from an n = 1 state to an n = 3 state, how much energy does this correspond to? Is this an absorption or an emission? What is the wavelength of the photon involved in this process? To what region of the electromagnetic spectrum does this correspond?
-
The hydrogen atom emits a photon with a 486 nm wavelength, corresponding to an electron decaying from the n = 4 level to which level? What is the color of the emission?
-
An electron in a hydrogen atom can decay from the n = 3 level to n = 2 level. What is the color of the emitted light? What is the energy of this transition?
-
Calculate the wavelength and energy of the photon that gives rise to the third line in order of increasing energy in the Lyman series in the emission spectrum of hydrogen. In what region of the spectrum does this wavelength occur? Describe qualitatively what the absorption spectrum looks like.
-
The wavelength of one of the lines in the Lyman series of hydrogen is 121 nm. In what region of the spectrum does this occur? To which electronic transition does this correspond?
-
Removing an electron from solid potassium requires 222 kJ/mol. Would you expect to observe a photoelectric effect for potassium using a photon of blue light (λ = 485 nm)? What is the longest wavelength of energy capable of ejecting an electron from potassium? What is the corresponding color of light of this wavelength?
-
The binding energy of an electron is the energy needed to remove an electron from its lowest energy state. According to Bohr’s postulates, calculate the binding energy of an electron in a hydrogen atom. There are 6.02 x 10 23 atoms in 1g of hydrogen atoms What wavelength in nanometers is required to remove such an electron from one hydrogen atom?
-
As a radio astronomer, you have observed spectral lines for hydrogen corresponding to a state with n = 320, and you would like to produce these lines in the laboratory. Is this feasible? Why or why not?
Numerical Answers
-
656 nm; red light
-
n = 2, blue-green light
-
97.2 nm, 2.04 × 10 −18 J/photon, ultraviolet light, absorption spectrum is a single dark line at a wavelength of 97.2 nm
-
Violet: 390 nm, 307 kJ/mol photons; Blue-purple: 440 nm, 272 kJ/mol photons; Blue-green: 500 nm, 239 kJ/mol photons; Orange: 580 nm, 206 kJ/mol photons; Red: 650 nm, 184 kJ/mol photons
-
1313 kJ/mol, λ ≤ 91.1 nm
The Wave Behavior of Matter
Conceptual Problems
-
Explain what is meant by each term and illustrate with a sketch:
- standing wave
- fundamental
- overtone
- node
-
How does Einstein’s theory of relativity illustrate the wave–particle duality of light? What properties of light can be explained by a wave model? What properties can be explained by a particle model?
-
In the modern theory of the electronic structure of the atom, which of de Broglie’s ideas have been retained? Which proved to be incorrect?
-
According to Bohr, what is the relationship between an atomic orbit and the energy of an electron in that orbit? Is Bohr’s model of the atom consistent with Heisenberg’s uncertainty principle? Explain your answer.
Numerical Problems
-
How much heat is generated by shining a carbon dioxide laser with a wavelength of 1.065 μm on a 68.95 kg sample of water if 1.000 mol of photons is absorbed and converted to heat? Is this enough heat to raise the temperature of the water by 4°C?
-
Show the mathematical relationship between energy and mass and between wavelength and mass. What is the effect of doubling the
- mass of an object on its energy?
- mass of an object on its wavelength?
- frequency on its mass?
-
What is the de Broglie wavelength of a 39 g bullet traveling at 1020 m/s ± 10 m/s? What is the minimum uncertainty in the bullet’s position?
-
What is the de Broglie wavelength of a 6800 tn aircraft carrier traveling at 18 ± 0.1 knots (1 knot = 1.15 mi/h)? What is the minimum uncertainty in its position?
-
Calculate the mass of a particle if it is traveling at 2.2 × 10 6 m/s and has a frequency of 6.67 × 10 7 Hz. If the uncertainty in the velocity is known to be 0.1%, what is the minimum uncertainty in the position of the particle?
-
Determine the wavelength of a 2800 lb automobile traveling at 80 mi/h ± 3%. How does this compare with the diameter of the nucleus of an atom? You are standing 3 in. from the edge of the highway. What is the minimum uncertainty in the position of the automobile in inches?
Numerical Answers
-
E = 112.3 kJ, Δ T = 0.3893°C, over ten times more light is needed for a 4.0°C increase in temperature
-
-
1.7 × 10 −35 m, uncertainty in position is ≥ 1.4 × 10 −34 m
-
-
9.1 × 10 −39 kg, uncertainty in position ≥ 2.6 m
Quantum Mechanics and Atomic Orbitals
Conceptual Problems
-
Why does an electron in an orbital with n = 1 in a hydrogen atom have lower energy than a free electron ( n = ∞)?
-
What four variables are required to fully describe the position of any object in space? In quantum mechanics, one of these variables is not explicitly considered. Which one and why?
-
Chemists generally refer to the square of the wave function rather than to the wave function itself. Why?
-
Orbital energies of species with only one electron are defined by only one quantum number. Which one? In such a species, is the energy of an orbital with n = 2 greater than, less than, or equal to the energy of an orbital with n = 4? Justify your answer.
-
In each pair of subshells for a hydrogen atom, which has the higher energy? Give the principal and the azimuthal quantum number for each pair.
- 1 s , 2 p
- 2 p , 2 s
- 2 s , 3 s
- 3 d , 4 s
-
What is the relationship between the energy of an orbital and its average radius? If an electron made a transition from an orbital with an average radius of 846.4 pm to an orbital with an average radius of 476.1 pm, would an emission spectrum or an absorption spectrum be produced? Why?
-
In making a transition from an orbital with a principal quantum number of 4 to an orbital with a principal quantum number of 7, does the electron of a hydrogen atom emit or absorb a photon of energy? What would be the energy of the photon? To what region of the electromagnetic spectrum does this energy correspond?
-
What quantum number defines each of the following?
- the overall shape of an orbital
- the orientation of an electron with respect to a magnetic field
- the orientation of an orbital in space
- the average energy and distance of an electron from the nucleus
-
In an attempt to explain the properties of the elements, Niels Bohr initially proposed electronic structures for several elements with orbits holding a certain number of electrons, some of which are in the following table:
Element Number of Electrons Electrons in orbits with n = 4 3 2 1 H 1 1 He 2 2 Ne 10 8 2 Ar 18 8 8 2 Li 3 1 2 Na 11 1 8 2 K 19 1 8 8 2 Be 4 2 2 - Draw the electron configuration of each atom based only on the information given in the table. What are the differences between Bohr’s initially proposed structures and those accepted today?
- Using Bohr’s model, what are the implications for the reactivity of each element?
- Give the actual electron configuration of each element in the table.
Numerical Problems
-
How many subshells are possible for n = 3? What are they?
-
How many subshells are possible for n = 5? What are they?
-
What value of l corresponds to a d subshell? How many orbitals are in this subshell?
-
What value of l corresponds to an f subshell? How many orbitals are in this subshell?
-
State the number of orbitals and electrons that can occupy each subshell.
- 2 s
- 3 p
- 4 d
- 6 f
-
State the number of orbitals and electrons that can occupy each subshell.
- 1 s
- 4 p
- 5 d
- 4 f
-
How many orbitals and subshells are found within the principal shell n = 6? How do these orbital energies compare with those for n = 4?
-
How many nodes would you expect a 4 p orbital to have? A 5 s orbital?
-
A p orbital is found to have one node in addition to the nodal plane that bisects the lobes. What would you predict to be the value of n ? If an s orbital has two nodes, what is the value of n ?
Numerical Answers
-
Three subshells, with l = 0 ( s ), l = 1 ( p ), and l = 2 ( d ).
-
-
A d subshell has l = 2 and contains 5 orbitals.
-
-
- 2 electrons; 1 orbital
- 6 electrons; 3 orbitals
- 10 electrons; 5 orbitals
- 14 electrons; 7 orbitals
-
-
A principal shell with n = 6 contains six subshells, with l = 0, 1, 2, 3, 4, and 5, respectively. These subshells contain 1, 3, 5, 7, 9, and 11 orbitals, respectively, for a total of 36 orbitals. The energies of the orbitals with n = 6 are higher than those of the corresponding orbitals with the same value of l for n = 4.
Many-Electron Atoms
Conceptual Problems
-
A set of four quantum numbers specifies each wave function. What information is given by each quantum number? What does the specified wave function describe?
-
List two pieces of evidence to support the statement that electrons have a spin.
-
The periodic table is divided into blocks. Identify each block and explain the principle behind the divisions. Which quantum number distinguishes the horizontal rows?
-
Identify the element with each ground state electron configuration.
- [He]2 s 2 2 p 3
- [Ar]4 s 2 3 d 1
- [Kr]5 s 2 4 d 10 5 p 3
- [Xe]6 s 2 4 f 6
-
Identify the element with each ground state electron configuration.
- [He]2 s 2 2 p 1
- [Ar]4 s 2 3 d 8
- [Kr]5 s 2 4 d 10 5 p 4
- [Xe]6 s 2
-
Propose an explanation as to why the noble gases are inert.
Numerical Problems
-
How many magnetic quantum numbers are possible for a 4 p subshell? A 3 d subshell? How many orbitals are in these subshells?
-
How many magnetic quantum numbers are possible for a 6 s subshell? A 4 f subshell? How many orbitals does each subshell contain?
-
If l = 2 and m l = 2, give all the allowed combinations of the four quantum numbers ( n , l , m l , m s ) for electrons in the corresponding 3 d subshell.
-
Give all the allowed combinations of the four quantum numbers ( n , l , m l , m s ) for electrons in a 4 d subshell. How many electrons can the 4 d orbital accommodate? How would this differ from a situation in which there were only three quantum numbers ( n , l , m )?
-
Given the following sets of quantum numbers ( n , l , m l , m s ), identify each principal shell and subshell.
- 1, 0, 0, ½
- 2, 1, 0, ½
- 3, 2, 0, ½
- 4, 3, 3, ½
-
Is each set of quantum numbers allowed? Explain your answers.
- n = 2; l = 1; m l = 2; m s = +½
- n = 3, l = 0; m l = −1; m s = −½
- n = 2; l = 2; m l = 1; m s = +½
- n = 3; l = 2; m l = 2; m s = +½
-
List the set of quantum numbers for each electron in the valence shell of each element.
- beryllium
- xenon
- lithium
- fluorine
-
List the set of quantum numbers for each electron in the valence shell of each element.
- carbon
- magnesium
- bromine
- sulfur
-
Sketch the shape of the periodic table if there were three possible values of m s for each electron (+½, −½, and 0); assume that the Pauli principle is still valid.
-
Predict the shape of the periodic table if eight electrons could occupy the p subshell.
-
If the electron could only have spin +½, what would the periodic table look like?
-
If three electrons could occupy each s orbital, what would be the electron configuration of each species?
- sodium
- titanium
- fluorine
- calcium
-
If Hund’s rule were not followed and maximum pairing occurred, how many unpaired electrons would each species have? How do these numbers compare with the number found using Hund’s rule?
- phosphorus
- iodine
- manganese
-
Write the electron configuration for each element in the ground state.
- aluminum
- calcium
- sulfur
- tin
- nickel
- tungsten
- neodymium
- americium
-
Write the electron configuration for each element in the ground state.
- boron
- rubidium
- bromine
- germanium
- vanadium
- palladium
- bismuth
- europium
-
Give the complete electron configuration for each element.
- magnesium
- potassium
- titanium
- selenium
- iodine
- uranium
- germanium
-
Give the complete electron configuration for each element.
- tin
- copper
- fluorine
- hydrogen
- thorium
- yttrium
- bismuth
-
Write the valence electron configuration for each element:
- samarium
- praseodymium
- boron
- cobalt
-
Using the Pauli exclusion principle and Hund’s rule, draw valence orbital diagrams for each element.
- barium
- neodymium
- iodine
-
Using the Pauli exclusion principle and Hund’s rule, draw valence orbital diagrams for each element.
- chlorine
- silicon
- scandium
-
How many unpaired electrons does each species contain?
- lead
- cesium
- copper
- silicon
- selenium
-
How many unpaired electrons does each species contain?
- helium
- oxygen
- bismuth
- silver
- boron
-
For each element, give the complete electron configuration, draw the valence electron configuration, and give the number of unpaired electrons present.
- lithium
- magnesium
- silicon
- cesium
- lead
-
Use an orbital diagram to illustrate the aufbau principle, the Pauli exclusion principle, and Hund’s rule for each element.
- carbon
- sulfur
Numerical Answers
-
For a 4 p subshell, n = 4 and l = 1. The allowed values of the magnetic quantum number, ml , are therefore +1, 0, −1, corresponding to three 4 p orbitals. For a 3 d subshell, n = 3 and l = 2. The allowed values of the magnetic quantum number, ml , are therefore +2, +1, 0, −1, −2, corresponding to five 3 d orbitals.


30.5: Fourth Species Counterpoint
30.5 Fourth Species Counterpoint
Fourth species deals with writing suspensions (and syncopations). Because this is only a brief introduction to species counterpoint, you will only encounter the cantus firmus in the lower voice in fourth species in this text. See the fourth species rules below.
- Start with a half rest, then write a half note an 8ve above the cantus firmus . The half note on the 3rd beat of every measure but the penultimate one ties across the barline to a half note on the first beat of the succeeding measure.
- End on a whole note at the interval of an 8ve above the cantus firmus .
- The penultimate measure should contain a 7-6 suspension.
- The half note on the third beat of each measure is always a consonance.
-
If the half note after a tie is a dissonance (4th or 7th), it is a suspension and
must resolve down by step
.
- Allowable suspensions in the upper part are 4-3 and 7-6; 9-8 and 2-1 are not allowed.
- If the half note after the tie is a consonance (1, 3, 5, 6, 8), it is a syncopation and can be left in any manner (by step or leap in any direction).
Notice that all suspensions and syncopations are labeled and all dissonant intervals are circled.
Go to Fourth Species Practice Exercises .


Skip to main content
-
Crohn’s disease
-
a chronic inflammatory disease that can cause ulcerations and fistulas in the intestines, particularly the colon and ileum
-
diverticulitis
-
inflammation of diverticula, which are bulging pouches that can form along the intestines
-
dysbiosis
-
imbalance of gut microbiota associated with an unhealthy outcome
-
galactosemia
-
a genetic disorder in which the galactose-1-phosphate uridyltransferase (GALT) enzyme is missing or does not function properly
-
hyperemesis gravidarum
-
persistent and severe vomiting caused by pregnancy; can lead to weight loss and dehydration
-
malabsorption
-
a digestive disorder that causes the body not to absorb nutrients from food effectively
-
microbiome
-
a collection of microorganisms that reside in the body, primarily in the gastrointestinal tract
-
necrotizing enterocolitis
-
a gastrointestinal tract disease in which the intestinal lining becomes inflamed, dies, and is sloughed off
-
prebiotic
-
nondigestible substances that stimulate growth of “good” gut bacteria
-
probiotic
-
foods that contain live microorganisms intended to maintain “good” gut bacteria
-
short bowel syndrome
-
a group of problems related to ineffective absorption of nutrients
-
ulcerative colitis (UC)
-
an inflammatory disease that affects the superficial lining of the large intestine, causing ulcerations


23.7: Accessory Organs in Digestion- The Liver, Pancreas, and Gallbladder
By the end of this section, you will be able to:
- State the main digestive roles of the liver, pancreas, and gallbladder
- Identify three main features of liver histology that are critical to its function
- Discuss the composition and function of bile
- Identify the major types of enzymes and buffers present in pancreatic juice
Chemical digestion in the small intestine relies on the activities of three accessory digestive organs: the liver, pancreas, and gallbladder (Figure \(\PageIndex{1}\) ). The digestive role of the liver is to produce bile and export it to the duodenum. The gallbladder primarily stores, concentrates, and releases bile. The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.
The Liver
The liver is the largest gland in the body, weighing about three pounds in an adult. It is also one of the most important organs. In addition to being an accessory digestive organ, it plays a number of roles in metabolism and regulation. The liver lies inferior to the diaphragm in the right upper quadrant of the abdominal cavity and receives protection from the surrounding ribs.
The liver is divided into two primary lobes: a large right lobe and a much smaller left lobe. In the right lobe, some anatomists also identify an inferior quadrate lobe and a posterior caudate lobe, which are defined by internal features. The liver is connected to the abdominal wall and diaphragm by five peritoneal folds referred to as ligaments. These are the falciform ligament, the coronary ligament, two lateral ligaments, and the ligamentum teres hepatis. The falciform ligament and ligamentum teres hepatis are actually remnants of the umbilical vein, and separate the right and left lobes anteriorly. The lesser omentum tethers the liver to the lesser curvature of the stomach.
The porta hepatis (“gate to the liver”) is where the hepatic artery and hepatic portal vein enter the liver. These two vessels, along with the common hepatic duct, run behind the lateral border of the lesser omentum on the way to their destinations. As shown in Figure \(\PageIndex{2}\), the hepatic artery delivers oxygenated blood from the heart to the liver. The hepatic portal vein delivers partially deoxygenated blood containing nutrients absorbed from the small intestine and actually supplies more oxygen to the liver than do the much smaller hepatic arteries. In addition to nutrients, drugs and toxins are also absorbed. After processing the bloodborne nutrients and toxins, the liver releases nutrients needed by other cells back into the blood, which drains into the central vein and then through the hepatic vein to the inferior vena cava. With this hepatic portal circulation, all blood from the alimentary canal passes through the liver. This largely explains why the liver is the most common site for the metastasis of cancers that originate in the alimentary canal.
Histology
The liver has three main components: hepatocytes, bile canaliculi, and hepatic sinusoids. A hepatocyte is the liver’s main cell type, accounting for around 80 percent of the liver's volume. These cells play a role in a wide variety of secretory, metabolic, and endocrine functions. Plates of hepatocytes called hepatic laminae radiate outward from the portal vein in each hepatic lobule .
Between adjacent hepatocytes, grooves in the cell membranes provide room for each bile canaliculus (plural = canaliculi). These small ducts accumulate the bile produced by hepatocytes. From here, bile flows first into bile ductules and then into bile ducts. The bile ducts unite to form the larger right and left hepatic ducts, which themselves merge and exit the liver as the common hepatic duct . This duct then joins with the cystic duct from the gallbladder, forming the common bile duct through which bile flows into the small intestine.
A hepatic sinusoid is an open, porous blood space formed by fenestrated capillaries from nutrient-rich hepatic portal veins and oxygen-rich hepatic arteries. Hepatocytes are tightly packed around the fenestrated endothelium of these spaces, giving them easy access to the blood. From their central position, hepatocytes process the nutrients, toxins, and waste materials carried by the blood. Materials such as bilirubin are processed and excreted into the bile canaliculi. Other materials including proteins, lipids, and carbohydrates are processed and secreted into the sinusoids or just stored in the cells until called upon. The hepatic sinusoids combine and send blood to a central vein . Blood then flows through a hepatic vein into the inferior vena cava. This means that blood and bile flow in opposite directions. The hepatic sinusoids also contain star-shaped reticuloendothelial cells (Kupffer cells), phagocytes that remove dead red and white blood cells, bacteria, and other foreign material that enter the sinusoids. The portal triad is a distinctive arrangement around the perimeter of hepatic lobules, consisting of three basic structures: a bile duct, a hepatic artery branch, and a hepatic portal vein branch.
Bile
Recall that lipids are hydrophobic, that is, they do not dissolve in water. Thus, before they can be digested in the watery environment of the small intestine, large lipid globules must be broken down into smaller lipid globules, a process called emulsification. Bile is a mixture secreted by the liver to accomplish the emulsification of lipids in the small intestine.
Hepatocytes secrete about one liter of bile each day. A yellow-brown or yellow-green alkaline solution (pH 7.6 to 8.6), bile is a mixture of water, bile salts, bile pigments, phospholipids (such as lecithin), electrolytes, cholesterol, and triglycerides. The components most critical to emulsification are bile salts and phospholipids, which have a nonpolar (hydrophobic) region as well as a polar (hydrophilic) region. The hydrophobic region interacts with the large lipid molecules, whereas the hydrophilic region interacts with the watery chyme in the intestine. This results in the large lipid globules being pulled apart into many tiny lipid fragments of about 1 µ m in diameter. This change dramatically increases the surface area available for lipid-digesting enzyme activity. This is the same way dish soap works on fats mixed with water.
Bile salts act as emulsifying agents, so they are also important for the absorption of digested lipids. While most constituents of bile are eliminated in feces, bile salts are reclaimed by the enterohepatic circulation . Once bile salts reach the ileum, they are absorbed and returned to the liver in the hepatic portal blood. The hepatocytes then excrete the bile salts into newly formed bile. Thus, this precious resource is recycled.
Bilirubin , the main bile pigment, is a waste product produced when the spleen removes old or damaged red blood cells from the circulation. These breakdown products, including proteins, iron, and toxic bilirubin, are transported to the liver via the splenic vein of the hepatic portal system. In the liver, proteins and iron are recycled, whereas bilirubin is excreted in the bile. It accounts for the green color of bile. Bilirubin is eventually transformed by intestinal bacteria into stercobilin, a brown pigment that gives your stool its characteristic color! In some disease states, bile does not enter the intestine, resulting in white (‘acholic’) stool with a high fat content, since virtually no fats are broken down or absorbed.
Hepatocytes work non-stop, but bile production increases when fatty chyme enters the duodenum and stimulates the secretion of the gut hormone secretin. Between meals, bile is produced but conserved. The valve-like hepatopancreatic ampulla closes, allowing bile to divert to the gallbladder, where it is concentrated and stored until the next meal.
Interactive Link
Watch this video to see the structure of the liver and how this structure supports the functions of the liver, including the processing of nutrients, toxins, and wastes. At rest, about 1500 mL of blood per minute flow through the liver. What percentage of this blood flow comes from the hepatic portal system?
The Pancreas
The soft, oblong, glandular pancreas lies transversely in the retroperitoneum behind the stomach. Its head is nestled into the “c-shaped” curvature of the duodenum with the body extending to the left about 15.2 cm (6 in) and ending as a tapering tail in the hilum of the spleen. It is a curious mix of exocrine (secreting digestive enzymes) and endocrine (releasing hormones into the blood) functions (Figure \(\PageIndex{3}\)).
The exocrine part of the pancreas arises as little grape-like cell clusters, each called an acinus (plural = acini), located at the terminal ends of pancreatic ducts. These acinar cells secrete enzyme-rich pancreatic juice into tiny merging ducts that form two dominant ducts. The larger duct fuses with the common bile duct (carrying bile from the liver and gallbladder) just before entering the duodenum via a common opening (the hepatopancreatic ampulla). The smooth muscle sphincter of the hepatopancreatic ampulla controls the release of pancreatic juice and bile into the small intestine. The second and smaller pancreatic duct, the accessory duct (duct of Santorini), runs from the pancreas directly into the duodenum, approximately 1 inch above the hepatopancreatic ampulla. When present, it is a persistent remnant of pancreatic development.
Scattered through the sea of exocrine acini are small islands of endocrine cells, the islets of Langerhans. These vital cells produce the hormones pancreatic polypeptide, insulin, glucagon, and somatostatin.
Pancreatic Juice
The pancreas produces over a liter of pancreatic juice each day. Unlike bile, it is clear and composed mostly of water along with some salts, sodium bicarbonate, and several digestive enzymes. Sodium bicarbonate is responsible for the slight alkalinity of pancreatic juice (pH 7.1 to 8.2), which serves to buffer the acidic gastric juice in chyme, inactivate pepsin from the stomach, and create an optimal environment for the activity of pH-sensitive digestive enzymes in the small intestine. Pancreatic enzymes are active in the digestion of sugars, proteins, and fats.
The pancreas produces protein-digesting enzymes in their inactive forms. These enzymes are activated in the duodenum. If produced in an active form, they would digest the pancreas (which is exactly what occurs in the disease, pancreatitis). The intestinal brush border enzyme enteropeptidase stimulates the activation of trypsin from trypsinogen of the pancreas, which in turn changes the pancreatic enzymes procarboxypeptidase and chymotrypsinogen into their active forms, carboxypeptidase and chymotrypsin.
The enzymes that digest starch (amylase), fat (lipase), and nucleic acids (nuclease) are secreted in their active forms, since they do not attack the pancreas as do the protein-digesting enzymes.
Pancreatic Secretion
Regulation of pancreatic secretion is the job of hormones and the parasympathetic nervous system. The entry of acidic chyme into the duodenum stimulates the release of secretin, which in turn causes the duct cells to release bicarbonate-rich pancreatic juice. The presence of proteins and fats in the duodenum stimulates the secretion of CCK, which then stimulates the acini to secrete enzyme-rich pancreatic juice and enhances the activity of secretin. Parasympathetic regulation occurs mainly during the cephalic and gastric phases of gastric secretion, when vagal stimulation prompts the secretion of pancreatic juice.
Usually, the pancreas secretes just enough bicarbonate to counterbalance the amount of HCl produced in the stomach. Hydrogen ions enter the blood when bicarbonate is secreted by the pancreas. Thus, the acidic blood draining from the pancreas neutralizes the alkaline blood draining from the stomach, maintaining the pH of the venous blood that flows to the liver.
The Gallbladder
The gallbladder is 8–10 cm (~3–4 in) long and is nested in a shallow area on the posterior aspect of the right lobe of the liver. This muscular sac stores, concentrates, and, when stimulated, propels the bile into the duodenum via the common bile duct. It is divided into three regions. The fundus is the widest portion and tapers medially into the body, which in turn narrows to become the neck. The neck angles slightly superiorly as it approaches the hepatic duct. The cystic duct is 1–2 cm (less than 1 in) long and turns inferiorly as it bridges the neck and hepatic duct.
The simple columnar epithelium of the gallbladder mucosa is organized in rugae, similar to those of the stomach. There is no submucosa in the gallbladder wall. The wall’s middle, muscular coat is made of smooth muscle fibers. When these fibers contract, the gallbladder’s contents are ejected through the cystic duct and into the bile duct (Figure \(\PageIndex{4}\)). Visceral peritoneum reflected from the liver capsule holds the gallbladder against the liver and forms the outer coat of the gallbladder. The gallbladder's mucosa absorbs water and ions from bile, concentrating it by up to 10-fold.


8.2: What is the Media?
-
- Last updated
- Save as PDF
Learning Objectives
By the end of this section, you will be able to:
- Explain what the media are and how they are organized
- Describe the main functions of the media in a free society
- Compare different media formats and their respective audiences
Ours is an exploding media system. What started as print journalism was subsequently supplemented by radio coverage, then network television, followed by cable television. Now, with the addition of the Internet, blogs and social media—a set of applications or web platforms that allow users to immediately communicate with one another—give citizens a wide variety of sources for instant news of all kinds. The Internet also allows citizens to initiate public discussion by uploading images and video for viewing, such as videos documenting interactions between citizens and the police, for example. Provided we are connected digitally, we have a bewildering amount of choices for finding information about the world. In fact, some might say that compared to the tranquil days of the 1970s, when we might read the morning newspaper over breakfast and take in the network news at night, there are now too many choices in today’s increasingly complex world of information. This reality may make the news media all the more important to structuring and shaping narratives about U.S. politics. Or the proliferation of competing information sources like blogs and social media may actually weaken the power of the news media relative to the days when news media monopolized our attention.
Media Basics
The term media defines a number of different communication formats from television media, which share information through broadcast airwaves, to print media, which rely on printed documents. The collection of all forms of media that communicate information to the general public is called mass media, including television, print, radio, and Internet. One of the primary reasons citizens turn to the media is for news. We expect the media to cover important political and social events and information in a concise and neutral manner.
To accomplish its work, the media employs a number of people in varied positions. Journalists and reporters are responsible for uncovering news stories by keeping an eye on areas of public interest, like politics, business, and sports. Once a journalist has a lead or a possible idea for a story, he or she researches background information and interviews people to create a complete and balanced account. Editors work in the background of the newsroom, assigning stories, approving articles or packages, and editing content for accuracy and clarity. Publishers are people or companies that own and produce print or digital media. They oversee both the content and finances of the publication, ensuring the organization turns a profit and creates a high-quality product to distribute to consumers. Producers oversee the production and finances of visual media, like television, radio, and film.
The work of the news media differs from public relations, which is communication carried out to improve the image of companies, organizations, or candidates for office. Public relations is not a neutral information form. While journalists write stories to inform the public, a public relations spokesperson is paid to help an individual or organization get positive press. Public relations materials normally appear as press releases or paid advertisements in newspapers and other media outlets. Some less reputable publications, however, publish paid articles under the news banner, blurring the line between journalism and public relations.
Media Types
Each form of media has its own complexities and is used by different demographics. Millennials (currently aged 18–33) are more likely to get news and information from social media, such as YouTube, Twitter, and Facebook, while baby boomers (currently aged 50–68) are most likely to get their news from television, either national broadcasts or local news (Figure 8.2).
Television alone offers viewers a variety of formats. Programming may be scripted, like dramas or comedies. It may be unscripted, like game shows or reality programs, or informative, such as news programming. Although most programs are created by a television production company, national networks—like CBS or NBC—purchase the rights to programs they distribute to local stations across the United States. Most local stations are affiliated with a national network corporation, and they broadcast national network programming to their local viewers.
Before the existence of cable and fiber optics, networks needed to own local affiliates to have access to the local station’s transmission towers. Towers have a limited radius, so each network needed an affiliate in each major city to reach viewers. While cable technology has lessened networks’ dependence on aerial signals, some viewers still use antennas and receivers to view programming broadcast from local towers.
Affiliates, by agreement with the networks, give priority to network news and other programming chosen by the affiliate’s national media corporation. Local affiliate stations are told when to air programs or commercials, and they diverge only to inform the public about a local or national emergency. For example, ABC affiliates broadcast the popular television show Once Upon a Time at a specific time on a specific day. Should a fire threaten homes and businesses in a local area, the affiliate might preempt it to update citizens on the fire’s dangers and return to regularly scheduled programming after the danger has ended.
Most affiliate stations will show local news before and after network programming to inform local viewers of events and issues. Network news has a national focus on politics, international events, the economy, and more. Local news, on the other hand, is likely to focus on matters close to home, such as regional business, crime, sports, and weather. 5 The NBC Nightly News , for example, covers presidential campaigns and the White House or skirmishes between North Korea and South Korea, while the NBC affiliate in Los Angeles (KNBC-TV) and the NBC affiliate in Dallas (KXAS-TV) report on the governor’s activities or weekend festivals in the region.
Cable programming offers national networks a second method to directly reach local viewers. As the name implies, cable stations transmit programming directly to a local cable company hub, which then sends the signals to homes through coaxial or fiber optic cables. Because cable does not broadcast programming through the airwaves, cable networks can operate across the nation directly without local affiliates. Instead they purchase broadcasting rights for the cable stations they believe their viewers want. For this reason, cable networks often specialize in different types of programming.
The Cable News Network (CNN) was the first news station to take advantage of this specialized format, creating a 24-hour news station with live coverage and interview programs. Other news stations quickly followed, such as MSNBC and FOX News. A viewer might tune in to Nickelodeon and catch family programs and movies or watch ESPN to catch up with the latest baseball or basketball scores. The Cable-Satellite Public Affairs Network, known better as C-SPAN, now has three channels covering Congress, the president, the courts, and matters of public interest.
Cable and satellite providers also offer on-demand programming for most stations. Citizens can purchase cable, satellite, and Internet subscription services (like Netflix) to find programs to watch instantly, without being tied to a schedule. Initially, on-demand programming was limited to rebroadcasting old content and was commercial-free. Yet many networks and programs now allow their new programming to be aired within a day or two of its initial broadcast. In return they often add commercials the user cannot fast-forward or avoid. Thus networks expect advertising revenues to increase. 6
The on-demand nature of the Internet has created many opportunities for news outlets. While early media providers were those who could pay the high cost of printing or broadcasting, modern media require just a URL and ample server space. The ease of online publication has made it possible for more niche media outlets to form. The websites of the New York Times and other newspapers often focus on matters affecting the United States, while channels like BBC America present world news. FOX News presents political commentary and news in a conservative vein, while the Internet site Daily Kos offers a liberal perspective on the news. Politico.com is perhaps the leader in niche journalism.
Unfortunately, the proliferation of online news has also increased the amount of poorly written material with little editorial oversight, and readers must be cautious when reading Internet news sources. Sites like Buzzfeed allow members to post articles without review by an editorial board, leading to articles of varied quality and accuracy. The Internet has also made publication speed a consideration for professional journalists. No news outlet wants to be the last to break a story, and the rush to publication often leads to typographical and factual errors. Even large news outlets, like the Associated Press, have published articles with errors in their haste to get a story out.
The Internet also facilitates the flow of information through social media, which allows users to instantly communicate with one another and share with audiences that can grow exponentially. Facebook and Twitter have millions of daily users. Social media changes more rapidly than the other media formats. While people in many different age groups use sites like Facebook, Twitter, and YouTube, other sites like Snapchat and TikTok appeal mostly to younger users. The platforms also serve different functions. Tumblr and Reddit facilitate discussion that is topic-based and controversial, while Instagram is mostly social. A growing number of these sites also allow users to comment anonymously, leading to increases in threats and abuse. The 2020 QAnon conspiracy, which absurdly alleged a connection between liberal elites and child sex trafficking, was promulgated in part through social media posts on many platforms, including Facebook and Twitter. Both companies attempted to kick QAnon off their platforms. 7
Regardless of where we get our information, the various media avenues available today, versus years ago, make it much easier for everyone to be engaged. The question is: Who controls the media we rely on? Most media are controlled by a limited number of conglomerates. A conglomerate is a corporation made up of a number of companies, organizations, and media networks. In the 1980s, more than fifty companies owned the majority of television and radio stations and networks. By 2011, six conglomerates controlled most of the broadcast media in the United States: CBS Corporation, Comcast, Time Warner, 21st Century Fox (formerly News Corporation), Viacom, and The Walt Disney Company (Figure 8.3). 8 With the Disney-Fox merger in March 2019 and the CBS-Viacom merger in December 2019, this number was reduced to four. Moreover, these conglomerates own much of the airways for television news. The Walt Disney Company also owns the ABC Television Network, ESPN, A&E, and Lifetime, in addition to the Disney Channel and Disney+, a popular streaming service. Viacom also owns BET, Comedy Central, MTV, Nickelodeon, and VH1. Warner Bros. Discovery owns Cartoon Network, CNN, HBO, Food Network, and HGTV among others. While each of these networks has its own programming, in the end, the conglomerate can make a policy that affects all stations and programming under its control.
Link to Learning
If you are concerned about the lack of variety in the media and the market dominance of media conglomerates, the non-profit organization, Free Press , tracks and promotes open communication.
These changes in the format and ownership of media raise the question whether the media still operate as an independent source of information. Is it possible that corporations and CEOs now control the information flow, making profit more important than the impartial delivery of information? The reality is that media outlets, whether newspaper, television, radio, or Internet, are businesses. They have expenses and must raise revenues. Yet at the same time, we expect the media to entertain, inform, and alert us without bias. They must provide some public services, while following laws and regulations. Reconciling these goals may not always be possible.
Functions of the Media
The media exist to fill a number of functions. Whether the medium is a newspaper, a radio, or a television newscast, a corporation behind the scenes must bring in revenue and pay for the cost of the product. Revenue comes from advertising and sponsors, like McDonald’s, Ford Motor Company, and other large corporations. But corporations will not pay for advertising if there are no viewers or readers. So all programs and publications need to entertain, inform, or interest the public and maintain a steady stream of consumers. In the end, what attracts viewers and advertisers is what survives.
The media are also watchdogs of society and of public officials. Some refer to the media as the fourth estate , with the branches of government being the first three estates and the media equally participating as the fourth. This role helps maintain democracy and keeps the government accountable for its actions, even if a branch of the government is reluctant to open itself to public scrutiny. As much as social scientists would like citizens to be informed and involved in politics and events, the reality is that we are not. So the media, especially journalists, keep an eye on what is happening and sounds an alarm when the public needs to pay attention. 11
The media also engages in agenda setting , which is the act of choosing which issues or topics deserve public discussion. For example, in the early 1980s, famine in Ethiopia drew worldwide attention, which resulted in increased charitable giving to the country. Yet the famine had been going on for a long time before it was discovered by western media. Even after the discovery, it took video footage to gain the attention of the British and U.S. populations and start the aid flowing. 12 Today, numerous examples of agenda setting show how important the media are when trying to prevent further emergencies or humanitarian crises. In the spring of 2015, when the Dominican Republic was preparing to exile Haitians and undocumented (or under documented) residents, major U.S. news outlets remained silent. However, once the story had been covered several times by Al Jazeera, a state-funded broadcast company based in Qatar, ABC, the New York Times , and other network outlets followed. 13 With major network coverage came public pressure for the U.S. government to act on behalf of the Haitians. 14
Insider Perspective
Christiane Amanpour on “What Should Be News?”
The media are our connection to the world. Some events are too big to ignore, yet other events, such as the destruction of Middle Eastern monuments or the plight of foreign refugees, are far enough from our shores that they often go unnoticed. What we see is carefully selected, but who decides what should be news?
As the chief international correspondent for CNN, Christiane Amanpour is one media decision maker (Figure 8.4). Over the years, Amanpour has covered events around the world from war to genocide. In an interview with Oprah Winfrey, Amanpour explains that her duty, and that of other journalists, is to make a difference in the world. To do that, “we have to educate people and use the media responsibly.” 15 Journalists cannot passively sit by and wait for stories to find them. “Words have consequences: the stories we decide to do, the stories we decide not to do . . . it all matters.” 16
As Amanpour points out, journalists are often “on the cutting edge of reform,” so if they fail to shed light on events, the results can be tragic. One of her biggest regrets was not covering the genocide in Rwanda in 1994, which cost nearly a million lives. She said the media ignored the event in favor of covering democratic elections in South Africa and a war in Bosnia, and ultimately she believes the media failed the people. “If we don’t respect our profession and we see it frittering away into the realm of triviality and sensationalism, we’ll lose our standing,” she said. “That won’t be good for democracy. A thriving society must have a thriving press.”
This feeling of responsibility extends to covering moral topics, like genocide. Amanpour feels there shouldn’t be equal time given to all sides. “I’m not just a stenographer or someone with a megaphone; when I report, I have to do it in context, to be aware of the moral conundrum. . . . I have to be able to draw a line between victim and aggressor.”
Amanpour also believes the media should cover more. When given the full background and details of events, society pays attention to the news. “Individual Americans had an incredible reaction to the [2004 Indian Ocean] tsunami—much faster than their government’s reaction,” she said. “Americans are a very moral and compassionate people who believe in extending a helping hand, especially when they get the full facts instead of one-minute clips.” If the news fulfills its responsibility, as she sees it, the world can show its compassion and help promote freedom.
Why does Amanpour believe the press has a responsibility to report all that they see? Are there situations in which it is acceptable to display partiality in reporting the news? Why or why not?
Before the Internet, traditional media determined whether citizen photographs or video footage would become “news.” In 1991, a private citizen’s camcorder footage showed four police officers beating an African American motorist named Rodney King in Los Angeles. After appearing on local independent television station, KTLA-TV, and then the national news, the event began a national discussion on police brutality and ignited riots in Los Angeles. 17 The agenda-setting power of traditional media has begun to be appropriated by social media and smartphones, however. Tumbler, Facebook, YouTube, and other Internet sites allow witnesses to instantly upload images and accounts of events and forward the link to friends. Some uploads go viral and attract the attention of the mainstream media, but large network newscasts and major newspapers are still more powerful at initiating or changing a discussion.
The media also promote the public good by offering a platform for public debate and improving citizen awareness. Network news informs the electorate about national issues, elections, and international news. The New York Times , Los Angeles Times , NBC Nightly News , and other outlets make sure voters can easily find out what issues affect the nation. Is terrorism on the rise? Is the dollar weakening? The network news hosts national debates during presidential elections, broadcasts major presidential addresses, and interviews political leaders during times of crisis. Cable news networks now provide coverage of all these topics as well.
Local news has a larger job, despite small budgets and fewer resources (Figure 8.5). Local government and local economic policy have a strong and immediate effect on citizens. Is the city government planning on changing property tax rates? Will the school district change the way Common Core tests are administered? When and where is the next town hall meeting or public forum to be held? Local and social media provide a forum for protest and discussion of issues that matter to the community.
Link to Learning
Want a snapshot of local and state political and policy news? The magazine Governing keeps an eye on what is happening in each state, offering articles and analysis on events that occur across the country.
While journalists reporting the news try to present information in an unbiased fashion, sometimes the public seeks opinion and analysis of complicated issues that affect various populations differently, like healthcare reform and the Affordable Care Act. This type of coverage may come in the form of editorials, commentaries, Op-Ed columns, and blogs. These forums allow the editorial staff and informed columnists to express a personal belief and attempt to persuade. If opinion writers are trusted by the public, they have influence.
Walter Cronkite, reporting from Vietnam, had a loyal following. In a broadcast following the Tet Offensive in 1968, Cronkite expressed concern that the United States was mired in a conflict that would end in a stalemate. 18 His coverage was based on opinion after viewing the war from the ground. 19 Although the number of people supporting the war had dwindled by this time, Cronkite’s commentary bolstered opposition. Like editorials, commentaries contain opinion and are often written by specialists in a field. Larry Sabato, a prominent political science professor at the University of Virginia, occasionally writes his thoughts for the New York Times . These pieces are based on his expertise in politics and elections. 20 Blogs offer more personalized coverage, addressing specific concerns and perspectives for a limited group of readers. As of 2021, the most popular blog on U.S. politics was The Daily Kos , a liberal blog with 25 million followers each month. 21


6.2: Gaining Advantages by Understanding the Competitive Environment
- What is strategic analysis, and why do firms need to analyze their competitive environment?
Strategic analysis is the process that firms use to study and understand the many different layers and aspects of their competitive environment. Why do firms spend time and money trying to understand what is going on around them? Firms do not operate in a vacuum. They are impacted by forces and factors from inside their organizations and outside in the world at large. Understanding these forces and factors is crucial to achieving success as a business. For example, the growth in the Spanish-speaking population in the United States has led many firms to change the signage in their stores and labels on their products to include Spanish, in order to make their stores easier to shop in and their products easier to identify for this growing market. The external environment is continually changing, and the most successful firms are able to prepare for and adapt to environmental changes because they have done their homework and understand how external forces impact their operations.
To react to change more easily and develop products consumers want, managers and consultants engage in environmental scanning —the systematic and intentional analysis of both a firm’s internal state and its external, competitive environment. From a local coffee shop to an international corporation, firms of all sizes benefit from strategic analysis. Let’s examine some important strategic factors in more detail.
The Competitive Environment
A firm’s competitive environment includes components inside the firm and outside the firm. External factors are things in the global environment that may impact a firm’s operations or success, examples are a rise in interest rates, or a natural disaster. External factors cannot be controlled, but they must be managed effectively, and to understand them so that the firm can be as successful. For example, the unemployment rate will affect a firm’s ability to hire qualified employees at a reasonable rate of pay. If unemployment is high, meaning that a lot of people are looking for jobs, then a firm will probably have a lot of applicants for any positions it needs to fill. It will be able to choose more highly qualified applicants to hire and may be able to hire them at a lower pay rate because the employee would rather work for a lower pay rate than not have a job at all. On the other hand, when unemployment is low, meaning that not many people are looking for jobs, firms may have to offer higher pay or settle for lower qualifications to find someone to fill a position.
Internal factors are characteristics of the firm itself. To plan to compete against other firms, a firm needs to understand what physical, financial, and human resources it has, what it is good at, and how it is organized. For example, Walmart has a sophisticated IT system that tracks inventory and automatically orders products before they run out, by calculating how long it will take for the new product to arrive and comparing that to the rate at which the product is selling off the shelves. The system orders new product so that it will arrive just as the product on the shelves is running out, so that Walmart stores do not need to have storage space for inventory. All Walmart inventory is on the store shelves, ready to be sold to customers. How does this system benefit Walmart? It does not have to spend money on storing or keeping track of inventory, all products in the store can generate revenue because they are available for customers to buy, and when the system is working optimally, the store never runs out of items customers want.
- Why do managers use strategic analysis?
- How are internal factors different from external factors in a firm’s competitive environment?