Discussion
In the night vision apparatus which type of waves are used?
Answer: B
Night vision apparatus uses infrared rays.
All warm bodies, people and animals included, give off infrared radiation. Thermal night vision devices detect this infrared and build an image from it, and image-intensifier devices are also sensitive to near-infrared light, which is why many carry an infrared illuminator. Infrared needs no visible light, so it works in darkness.
Ultraviolet rays are not emitted by warm bodies in useful amounts and are absorbed by most lenses. X-rays are used to see inside bodies, not in the dark. Beta rays are streams of electrons from radioactive decay, not waves used for vision.
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