^Wave optics

Light behaves as a wave when the size of obstacle is comparable with the wavelength of light. Wave optics branch explains the following phenomena

1. Interference (i.e. non uniform distribution of energy when two or more light waves superpose)
2. Diffraction (i.e. bending & spreading of light wavefronts on encountering obstructions of size comparable or smaller than its wavelength)
3. Polarisation (i.e. restricting the vibrations of light to one plane)