Reflection, Refraction & Transmission
- When waves arrive at a boundary between two materials, they can be:
- Reflected
- Refracted
- Transmitted
- Absorbed
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
Refraction
- 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 decreases in the shallower water
- This is because the waves cannot travel as deep into the water as there is less 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 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
