Electromagnetic Radiation

Electromagnetic radiation (EM) is light. It is characterized by its frequency and wavelength (next section). When you consider all the possibilities you have the entire electromagnetic spectrum. It is broken up into zones that each have a specific name. Here is a very nice wikipedia graphic showing this.


You need to memorize a few things here. First memorize the order of the seven various regions/bands/zones within the entire range. In order from highest energy down to lowest energy is gamma rays, x-rays, ultra violet, visible, infra-red, microwaves, radio waves. Second, memorize the two ends of the visible spectrum. We do the following to make this an easier thing... the highest energy end is the "blue" end at 400 nm, the lowest energy end is the "red" end at 700 nm. So we "say" visible light is from 400-700 nm, blue to red. 400 nm is actually more violet than blue, but we call it the blue end nonetheless.

Roy G. Biv

Memorize the order of the colors of the visible spectrum as well. Roy G. Biv helps a lot here. Red, orange, yellow, green, blue, indigo, and violet. This is also the colors of the rainbow in the right order.

We will further break up some other zones as well. We will learn the differences in UV-A, UV-B, and UV-C in section 3.4 of this chapter. For now, get the visible straight and the ordering of the various bands.

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