Reflection, Refraction & Diffraction
- All waves, whether transverse or longitudinal, can be reflected, refracted and diffracted
Reflection
- Reflection occurs when:
A wave hits a boundary between two media and does not pass through, but instead stays in the original medium
- The law of reflection states:
The angle of incidence = The angle of reflection
- When waves hit an object, such as a barrier, they can be reflected:
Reflection
When waves reflect off a barrier, the angle of reflection, r, is equal to the angle of incidence, i
Refraction
- Refraction occurs when:
A wave passes a boundary between two different transparent media and undergoes a change in direction
- When waves enter a different medium, their speed can change
- This effect is called refraction, and it can have two other effects:
- The wavelength of the waves can increase or decrease
- The waves can change direction
Refraction
Waves can change direction when moving between materials with different densities
- If the waves slow down, the waves will bunch together, causing the wavelength to decrease
- The waves will also start to turn slightly towards the normal
- If the waves speed up then they will spread out, causing the wavelength to increase
- The waves will also turn slightly away from the normal
Diffraction
- When waves pass through a narrow gap, the waves spread out
- This effect is called diffraction
Diffraction
Diffraction: when a wave passes through a narrow gap, it spreads out
Exam Tip
When drawing waves being reflected take care to:
- Make sure that the angle of incidence is equal to the angle of reflection
- Keep the wavelength of the waves the same
Similarly, when waves are diffracted the wavelength remains constant.
Refraction is the only wave effect in which the wavelength changes.
Remember:
Refraction is the name given to the change in the speed of a wave when it passes from one medium to another. The change in direction is a consequence of this.
