Reflection, Refraction & Transmission (HL IB Physics)

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

Reflection

• 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
• During reflection, the frequency, wavelength and speed of the wave does not change

Refraction

• When light crosses the boundary between two media with different optical densities, it refracts
• Refraction occurs when:

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

Refraction of a ray between water and air

• 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
• In this case, water is denser than air
• 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

• An example of water waves refracting is when they travel from deeper to shallower water
  • The wavelength of the waves decreases in the shallower water

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

Transmission

• Transmission occurs when:

A wave passes through a substance

• Refraction is a type of transmission
  • Transmission is the more general term for 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 can be 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

• During transmission, the frequency or speed of the wave does not change

• Reflection, refraction and transmission occur for all types of waves, both transverse and  longitudinal