Refraction of Light (SQA National 5 Physics): Revision Note

Refraction of light

• Refraction is defined as:

The change in direction of a ray of light when it travels from one medium to another

• Refraction of a wave occurs because the wave changes velocity upon entering a new medium

• If the waves slow down upon entering the new medium:

  • the wavefronts will cover less distance in the same amount of time

  • the wavefronts bunch together and the wavelength decreases

  • the wavefronts will bend towards the normal

• If the waves speed up upon entering a new medium:

  • the wavefronts will cover more distance in the same amount of time

  • the wavefronts spread out and the wavelength increases

  • the wavefronts will bend away from the normal

• The speed of the wave will only change if the ray approaches the boundary at an angle

  • When the wave enters the new medium perpendicularly, the ray will not change direction