Class 12 Physics Electromagnetic Waves Ultraviolet rays

Ultraviolet rays(UV rays)

It covers wavelengths ranging from about 4 × 10–7 m (400 nm) down to 6 × 10–10m (0.6 nm).

  • The UVrays are produced by special lamps and very hot bodies (sun).
  • UV rays have harmful effects on humans.
  • UV lamps are used to kill germs in water purifiers.
  • For example:-
    • When UV rays fall on the skin of humans then it leads to the production of a pigment called melamine which causes tanning of the skin.
  • In order to protect from UV rays glasses are used,as they get absorbed by the glasses.
  • UV rays help in LASER assisted eye surgery.
    • As UV rays have very short wavelength so they can be focussed into narrow beam of light.


  • The ozone layerwhich is present outside the atmosphere protects us from the harmful UV rays.
  • Ozone has a property of reflecting the harmful UV rays.
    • But due to the use of CFC (chlorofluorocarbon) ozone layer is depleting.
    • So if ozone layer gets depleted humans will get exposed to harmful UV rays coming from the sun.

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