Define each of the following wave phenomena, and give an example of where each occurs: (a) refraction; (b) diffraction; (c) dispersion; (d) interference.

Refraction is the phenomenon of change in speed of light when the light when it passes from the medium of one optical density to a medium of another optical density. The light rays also show a bending when passing through the interface of such medium. Diffraction is the process of spreading of the light or any system of wave after passing through a narrow gap of the order of wavelength of the wave. Dispersion is the phenomenon of acquiring the velocity corresponding to its wavelength by a wave. Interference of waves is the phenomenon of interaction of of two waves when they meet and superimpose on one another to give a wave of resultant properties of both the source waves.