Refraction (Edexcel GCSE Physics: Combined Science)

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Refraction

  • Refraction can occur when a wave crosses a boundary between two materials with different densities
  • In some cases, the wave will change direction
  • The ray diagram below illustrates the change of direction of a light ray at a water-air boundary:

Refraction direction change, downloadable IGCSE & GCSE Physics revision notes

Waves can change direction when moving between materials with different densities

Refraction of light

  • Refraction also occurs when light passes a boundary between two different transparent media
  • At the boundary, the rays of light undergo a change in direction
  • The direction is taken as the angle from the normal
  • The change in direction depends on the difference in density between the two media:
    • From less dense to more dense (e.g air to glass), light bends towards the normal
    • From more dense to less dense (e.g. glass to air), light bends away from the normal
    • When passing along the normal (perpendicular) the light does not bend at all

Refraction of Light Through a Glass Block

Refraction of Light, downloadable IGCSE & GCSE Physics revision notes

Light enters the glass where the light ray bends towards the normal. Light bends away from the normal as it exits the glass 

  • The change in direction occurs due to the change in speed when travelling in different substances
    • When light passes into a denser substance the rays will slow down, hence they bend towards the normal

  • As with refraction of water waves, the only properties that change during refraction of light are speed and wavelength – the frequency of waves does not change
    • Different frequencies account for different colours of light (red has a low frequency, whilst blue has a high frequency)
    • When light refracts, it does not change colour (think of a pencil in a glass of water), therefore, the frequency does not change

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Ashika

Author: Ashika

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.