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Introduction to Ultraviolet and Infrared Radiation

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

The short-wavelength range of ultraviolet radiation extends to 1 nanometer, with even shorter wavelengths belonging to X-rays. The wavelength range of infrared radiation extends to 1 millimeter (an artificially defined limit), with even longer wavelengths belonging to the radio wave domain.

Although both ultraviolet and infrared radiation are imperceptible to the eye, they can be physiologically detected. If the intensity is high enough, they can cause the skin to feel warm. This phenomenon strongly demonstrates that all radiation can generate heat when absorbed, and not just infrared radiation, as is commonly believed. Furthermore, ultraviolet radiation with wavelengths less than 320 nanometers is harmful to living tissue. For example, exposure to ultraviolet radiation on the skin can cause redness and blistering over a period of time.

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