The electromagnetic spectrum

“Radiowave, Microwave, Infra-red—–radiation…”

Generations of my students have been “forced” to listen to this song. I have only good intentions: I hope the chorus sticks in their mind so they have no problem recalling the order of the various members of the electromagnetic spectrum.

What our eyes detect, is actually a very very narrow range of wavelength: from the 400 nm violet to the 700 nm red. The brightness of the light is determined by the intensity (and hence amplitude-square) of the wave. (Our eyes cannot possibly follow the instantaneous electric-field strength which oscillates at hundreds of terahertz). The color we see is determined by the wavelength.

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