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.
There are three groupings of naturally occurring radiation, mostly based on where the radiation comes from. First there is the radiation in the soils and rocks, called primordial or terrestrial. Then there is radiation that comes from space, called cosmic or cosmogenic.aturally occurring radiation can be found all around us. Radiation can be found in soils, in our air and water, and in us. Because it occurs in our natural environment, we encounter it every day through the food we eat, the water we drink, and the air we breathe.