The size of the aperture (or object) determines the extent of diffraction, with the most significant diffraction occurring when the aperture is of the same order of magnitude as the wavelength of the wave. Diffractionĭiffraction is the spreading out of a wave when it passes through an aperture (gap/hole) or around an object. IMPORTANT NOTE: If a wave enters a medium at 90º to the surface (parallel to the normal) it is not refracted.

The angle of refraction is larger or smaller than the angle of incidence depending on how the speed changes:

Refraction occurs because waves travel at different speeds in different mediums and this change in speed is caused by differences in density between the mediums.