Revise GCSE Physics

Question:What is diffraction?

When a wave meets a partial obstruction or passes through a gap you would expect the obstructed part of the wave to be reflected and the unobstructed part of the wave to continue on unimpeded and unchanged.

Actually, as you can see from these diagrams, waves do not behave quite like that.

Angry face

Diffraction is the tendency of a wave to spread out as it passes an obstacle or through a gap.