Refraction

Refraction of Waves

Behaviour of Waves

• Slowing Down: When waves slow down, they bend towards the normal.
• Speeding Up: When waves speed up, they bend away from the normal.

Wavefront

Process of Refraction

Diagram Explanation

• The angle of Incidence (i): The angle between the incident wave and the normal.
• The angle of Refraction (r): The angle between the refracted wave and the normal.

Summary

Refraction occurs when waves change speed as they pass from one medium to another, causing them to change direction. The behaviour of the waves depends on whether they speed up or slow down.

Refraction

• General Rule:
  • If entering a denser material, it bends towards the normal.
  • If entering a less dense material, it bends away from the normal.

Interaction with EM Waves

Velocity Differences

• Some effects are due to differences in velocity:
  • When light enters a denser medium, it slows down.
  • Shorter wavelengths slow down more than longer wavelengths.

Dispersion

• Dispersion occurs when white light enters a prism:
  • Different wavelengths refract a different amount and therefore spread out creating a rainbow effect.
• When refracting, the speed decreases and the wavelength decreases too in denser material:
  • The horizontal lines show the "wavefronts" of the waves, with each line representing the peaks of the transverse wave.