Each case of communicable disease is the result of an orderly progression in. a series of events. This series of events may be described as a three-link chain, each. link representing a factor essential to the transmission of disease. These links (figure 1-1) are: (1) The source of the disease (reservoir) (2) The means by which the disease may be transmitted (mode of.
Radio Waves. Radio waves are a type of electromagnetic (EM) radiation with wavelengths in the electromagnetic spectrum longer than infrared light . They have have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves, radio waves travel at the speed of light. Naturally occurring radio waves are made by lightning or by astronomical objects.
The heaviest naturally occurring element is uranium, which has 92 protons. Its most common form, or isotope, has 146 neutrons. Scientists have also artificially created most of the other elements between uranium and element 118. The newest element was created in a particle accelerator in Dubna, Russia, that shot a beam of calcium-48 ions (containing 20 protons) into a target of californium 249, an artificial element with 98 protons (map of Russia).