Diffraction

Diffraction is the bending of waves round an obstacle or through a hole.

Diffraction experiments show that:
(a) the diffraction effects are greater for long wavelength waves
(b) the diffraction effects are greater for small holes
These effects are shown in the following diagrams.

If the wavelength of the waves is shorter the spreading effect (diffraction)is much smaller as well. This explains why television waves are much more difficult to receive in hilly areas than radio waves which have a longer wavelength and why the diffraction of light is so difficult to observe.