IB DP Physics: SL复习笔记4.4.1 Reflection, Refraction & Transmission

Reflection, Refraction & Transmission

  • When waves arrive at a boundary between two materials, they can be:
    • Reflected
    • Refracted
    • Transmitted
    • Absorbed


  • Reflection occurs when:

A wave hits a boundary between two media and does not pass through, but instead bounces back to the original medium

  • The law of reflection states:

The angle of incidence, i = The angle of reflection, r


Reflection of a wave at a boundary

  • When a wave is reflected, some of it may also be absorbed by the medium, transmitted through the medium, or polarised
  • At a boundary between two media, the incident ray is the ray that travels towards the boundary


  • Refraction occurs when:

A wave changes speed and direction at the boundary between two media

  • This is due to the density of the media
    • If the medium is more dense, the wave slows down
    • If the medium is less dense, the wave speeds up
  • When a wave refracts, its speed and wavelength change, but its frequency remains the same
    • This is noticeable by the fact that the colour of the wave does not change
  • Both transverse and longitudinal waves can refract
  • An example of water waves refracting is when they travel from deeper to shallower water
    • The wavelength of the waves decrease in the shallower water


Water waves being refracted at the boundary between deep and shallow water


  • Transmission occurs when:

A wave passes through a substance

  • Refraction is a type of transmission
    • Transmission is the more general term of a wave appearing on the opposite side of a boundary (the opposite of reflection)
    • Refraction is specifically the change in direction of a wave when it crosses a boundary between two materials that have a different density
  •  When passing through a material, waves are usually partially absorbed
  • The transmitted wave will have a lower amplitude if some absorption has occurred


When a wave passes through a boundary it may be absorbed and transmitted