0.01
10¹² Millimeter waves 0.1
10¹⁰ Microwaves, radar 1
10
10⁸ TV and FM radio 100
Short wave 1,000
10⁶ AM radio 10,000
Low frequency communications 100,000
10,000 = 10⁴ 1,000,000
These many kinds of rays and waves vary tremendously in the ways they
interact with matter. But they are all part of a single family. The only
difference among them, as with the colors of the rainbow, lies in their
wavelengths. In a few cases, as we shall see later, the mode of
generation is also different.
The band of radiation stretching from the infrared to cosmic rays has
been, up to now, largely the concern of physical scientists. Because of
their high frequencies, these radiations are generally handled, when
calculations or measurements must be made, in terms of wavelength. Radio
and microwaves[5], on the other hand, have been more in the domain of
communications engineers and are more likely to be discussed in terms of
frequency. Thus it is that your radio is marked off in kilocycles, or
thousands of cycles per second, while light is described as radiation in
the 4000 to 7000 angstrom band.
The relative newness of the various radiations has kept scientists busy
learning about them and, as information and experience have accumulated,
putting them to work.