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Ultraviolet and infrared radiation

Electromagnetic radiation with wavelengths beyond the purple and red ends of the visible spectrum is called ultraviolet radiation and infrared radiation, respectively.

The short-wave range of ultraviolet rays extends to 1 nanometer, and the shorter ones are x-rays; the infrared wavelength range extends to 1 mm (an artificially defined limit), and the longer ones belong to the field of radio waves. Although ultraviolet rays and infrared rays are not felt by the eyes, they can be felt physiologically. If the intensity is high enough, it will make the skin feel hot. This phenomenon strongly illustrates that all radiation can generate heat after being absorbed, and it is not generally believed that only infrared rays have a special heating effect.

In addition, ultraviolet radiation with a wavelength less than 320 nanometers is harmful to living tissues of organisms. For example, after the skin is exposed to ultraviolet rays, it will turn red and blister within a certain period of time.

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