Unit 3 Properties of waves


Refraction of light

  • Light rays can change direction when passing from one material into another because the rays move at different speeds in the two materials. refraction refraction
  • Notice that the angle of incidence i and the angle of refraction r always lie between the light beam and the normal.
  • A material in which light travels slowly is said to be optically dense.
  • When travelling from an optically less dense material to a more dense material (such as air to glass), light bends towards the normal (diagram on the left above).
  • When travelling from an optically more dense material to a less dense material (such as glass to air), light bends away from the normal (diagram on the right above).
  • When light enters a different material:
    • the frequency stays the same
    • the wavelength changes
    • the speed changes.

Top Tip

When a light ray travels along the normal from air into glass, it passes straight through (undeviated), but it slows down.

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