Due to difference in refractive index of a material for different wavelengths, the focal length will be different for different colours. This will cause a separation of parallel beam of white light. This phenomenon is known as chromatic aberration.

Polarisation is a property applying to transverse waves that specify the geometrical orientation of the oscillations.

When energy waves (such as light, sound, and various electromagnetic waves) are caused to depart from a straight path due to imperfections in the medium it is called Scattering.

Spherical aberration is present when the outer parts of a lens do not bring light rays into the same focus as the central part.