In the July Scientific American there is an article about using light for local wifi instead of radio. On p. 84 there is a sidebar comparing the two media, including several interesting statements:
High transfer rates for radio depend on dangerously high power levels.
Radio signals interfere with each other but photons do not.
Out of phase radio waves can cancel each other out, but "destructive interference is impossible with light."
I think this article would be a good discussion starter for my modern physics or waves course.
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