- When waves hit an object, such as a barrier, they can be reflected:
When waves reflect off a barrier, the angle of reflection, r, is equal to the angle of incidence, i
- When waves are reflection:
angle of incidence = angle of reflection
i = r
- 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
When water waves travel from deep areas to shallow areas they slow down
- If the waves slow down the waves will bunch together, causing the wavelength to decrease. The waves will also start to travel closer to 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
- When waves pass through a narrow gap, the waves spread out
- This effect is called diffraction
Diffraction: when a wave passes through a narrow gap, it spreads out
- Diffraction, as shown above, only generally happens when the gap is smaller than the wavelength of the wave
- As the gap gets bigger, the effect gradually gets less pronounced until, in the case that the gap is very much larger than the wavelength, the waves no longer spread out at all
The size of the gap (compared to the wavelength) affects how much the waves spread out
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 one wave effect where the wavelength changes.
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.