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Seeing in the Dark

Ever wonder how night vision goggles work? Seeing in the Dark, on today's Moment of Science.

Ever wonder how night vision goggles work? Seeing in the Dark, on today’s Moment of Science.

If you’ve ever worn night vision goggles, you know that everything appears to be red, white, orange, and kind of shimmering.

This is because you’re seeing your surroundings in terms of radiated infrared light. See, light travels as waves. The shorter the wavelength, the higher the energy. Our eyes see a certain range of wavelengths, and light with wavelengths that are longer than what we can see is called infrared light. There are different kinds of infrared light, but the kind that matters for night vision goggles is called thermal-infrared.

This is light given off by anything that uses energy and produces heat, or that continues to give off heat after the sun goes down. The goggles basically detect the heat and turn it into a visible image.

You see, there’s a lens that focuses thermal infrared light generated by whatever you’re looking at. A device amplifies and scans the light and then creates a sort of temperature map. A computer translates the map into electric impulses, which turn into a picture displayed on the screen you look into. Basically, you see heat outlines of the objects around you.

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