Infrared (IR) and ultraviolet (UV) radiation is just as vital for life on Earth as visible light. Above and below the band of visible radiation lie the infrared and ultraviolet ranges, both of them invisible to the human eye.

Infrared radiation

When infrared radiation encounters an object, it is absorbed and transformed into heat. Without this heat radiation from the sun, the Earth would be locked in eternal ice.

Thanks to this phenomenon, sunlight today is an increasingly important alternative energy source: solar technology and photovoltaics are based on it. The IR range encompasses wavelengths between 780 nanometres (nm) and one micrometre (µ).

Ultraviolet radiation

UV radiation is just as essential for life as IR radiation. It is divided – on the basis of its biological impacts – into three subtypes:

• UV-A radiation (315 nm to 380 nm) tans skin.
• UV-B radiation (280 nm to 315 nm) promotes Vitamin D production. Excessive exposure causes reddening of the skin (erythema) and sunburn.
• UV-C radiation (100 nm to 280 nm) destroys cells. It is used in bactericidal lamps as a means of disinfection.
  
  

UV radiation has lots of positive effects, e.g. the vitamin D production promoted by UV-B. However, too much of it can cause damage. The ozone layer of the atmosphere protects us from harmful UV radiation, particularly from UV-C. Ozone depletion (the ozone gap) has negative consequences for life on Earth.