Optics: Visible, infrared and ultraviolet


Optics: Visible, infrared and ultraviolet

Different behaviours of different lights viz. Visible, Infraredand Ultraviolet.

Ultraviolet is the big brother, having higher frequency and therefore higher energy compared to visible and infrared radiations.

But since wavelength is inversely proportional to frequency, the wavelength of ultraviolet radiations is smaller than those of visible and infrared.

Visible light is almost friendly with everyone but ultraviolet and infrared are very specific in choosing their friends. 

Infrared radiation is friendly with snakes while Ultraviolet radiation is friendly with spiders and many insects.

More information about:


  • It varies from 700 nm to 1 mm in wavelength and from 300 GHz to 400 THz in frequency.
  • This radiation can be focused, reflected and polarized like visible light.


  • These radiations are used in heat sensors, thermal imaging and night vision equipment.
  • These radiations are used in wired and wireless operations in communication and networking.
  • It is also used in fiber optic cables to transmit data.


  • Visible radiation varies from 380 nm to 740 nm in wavelength and from 430 THz to 770 THz in frequency.
  • The visible spectrum does not contain all the colours that a human eye and brain can distinguish such pink, purple, etc.


  • Visible spectrum lets human beings see the beauty of world.


  • This radiation varies from 400 nm to 10 nm in wavelength.
  • Maximum of the ultraviolet radiation is produced by sun.
  • In the laboratory,UV radiations are produced by the atomic excitation in a gaseous discharge tube.
  • It’s direct effects on human beings include reddening of the skin, pigmentation of skin and carcinogenic changes.


  • These radiations are used to kill microbes from water, surgical instruments etc.
  • These radiations are used in hospitals to sterilize the surgical equipments.
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