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Article: Refraction


Definition and Explanation of Refraction

  • Refraction is the redirection of a wave as it passes from one medium to another.
  • It can be caused by a change in the wave's speed or a change in the medium.
  • Light is the most commonly observed phenomenon of refraction.
  • Other waves, such as sound waves and water waves, also experience refraction.
  • Refraction occurs when a wave moves into a slower medium.
  • The wavefronts get compressed, causing the wave to change direction.
  • Light slows down in a medium due to the interaction of its electromagnetic waves with charged particles.
  • When light enters a slower medium at an angle, one side of the wavefront is slowed before the other, resulting in a change in angle of travel.
  • When light leaves the medium and returns to a vacuum, its speed returns to normal.

Role of Refraction in Optics

  • Optical prisms and lenses use refraction to redirect light.
  • The human eye also relies on refraction to focus light onto the retina.
  • The refractive index of materials varies with the wavelength of light.
  • This variation in refractive index causes dispersion, leading to the separation of white light into its constituent colors.
  • Instruments like glasses, cameras, binoculars, and microscopes are based on the principles of refraction.

Apparent Depth and Height

  • Rays of light from underwater objects appear to bend as they move from water to air.
  • The eye traces these rays back as straight lines, causing objects to appear higher or shallower than they actually are.
  • This phenomenon is known as apparent depth.
  • It affects activities like spearfishing and archery.
  • The ratio of apparent to real depth depends on the refractive indexes of air and water.


  • Refraction can cause the splitting of white light into a rainbow-spectrum when passing through a glass prism.
  • Different colors of light bend at different angles due to varying refractive indexes.
  • This phenomenon is known as dispersion.
  • It is responsible for rainbows and the colors we see in everyday life.
  • Dispersion can be observed when light passes from air to a material with a varying refractive index.

Atmospheric Refraction

  • Refractive index of air varies with temperature and pressure.
  • Lower pressure at higher altitudes causes light rays to refract towards the Earth's surface.
  • This phenomenon is known as atmospheric refraction.
  • It affects the apparent positions of stars near the horizon and the visibility of the sun during sunrise.
  • Temperature variations in the air can also cause refraction, leading to effects like heat haze and mirages.

Refraction Data Sources

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