How Everything Works
How Everything Works How Everything Works

Question 870

How can I make 1000 nanometer light waves visible to the human eye? — DMB, Broken Aarow, OK
Although our eyes are insensitive to 1000 nanometer infrared light, there are two ways to detect it effectively. The easiest is to use an inexpensive black-and-white surveillance video camera. Many of these cameras are sensitive to a broader spectrum of light than are our eyes and they can see 1000 nanometer light. If you check around, you should be able to find one that sees the light you're interested in. The other technique is to use a phosphorescent or "glow in the dark" material. When exposed to visible light, the atoms in such a material become trapped in electronic states that can emit visible light only after a very long random wait. But exposing a phosphorescent material to infrared light can shift the states of the atoms in the material to new states that can emit light immediately. Thus exposing some phosphorescent materials to infrared light causes them to emit light promptly. You can then see these materials glow particularly brightly after storing visible light energy in them and then exposing them to infrared light. However, they'll only glow briefly before you have to "recharge" them by exposing them to more visible light.

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