Class 12 Physics Electromagnetic Waves Infrared waves

Infrared waves

  • Infrared waves often known as heat waves as they are produced by hot bodies.
  • Their wavelength is lesser than both radio and micro waves.
  • They readily get absorbed by water.

Applications:- Infrared lamps/Infrared detector/LED in remote switches of electronic devices/Greenhouse effect.

For example:-

  1. Fire gives out both visible light waves and infrared waves.The light rays are visible to us but the infrared wavescannot be seen by us.
  2. Humans also generate some infrared waves.
  • There are some special glasses which have infrared detector to view infrared waves.
  • The infrared lamps are used to heat food materials and sometimes washrooms.
  • When we switch on the TV with the help of remote,there is an LED both on TV and on remote.
  • The signal gets transferred from remote to TV viainfrared waves.


Greenhouse Effect:- Green house effect is an atmospheric heating phenomenon that allows incoming solar radiation to pass through but blocks the heat radiated back from the Earth’s surface.

  • Consider that the sun gives radiation in the form of visible light to the earth.
  • When the visible light reaches the earth’s surface all the objects on the earth becomes hot.
  • The visible light carries energy from sun and that energy gets transferred to all the objects present on the earth.
  • As a result of heat transfer all the objects gets heated up.
  • These hot objects transmit infrared waves.
  • The earth will reradiate the infrared waves.
  • When these infrared waves try to go out of the atmosphere they get trapped by the greenhouse gases (CO2,CH4, water vapour).
  • As a result heat gets trapped inside the earth which results in an increase in temperature.
  • The greenhouse effect makes earth warm because of which the temperature of the earth is suitable for the survival of life on earth.
  • Global warming is due toan increase in temperature of the environment, due to pollution.

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