1) Reflection's quite straightforward, but there are other ways that waves can be made to change direction.
2) They can be refracted - which means they go through a new material but change direction.
3) Or they can be diffracted - the waves 'bend round' obstacles, causing the waves to spread out.
Diffraction - waves spreading out
1) All waves spread out ('diffract') at the edges when they pass through a gap or pass an obstacle.
2) The amount of diffraction depends on the size of the gap relative to the wavelength of the wave. The narrower the gap, or the longer the wavelength, the more the wave spreads out.
3) A narrower gap is one that is the same…