Wave optics describes the connection between waves and rays of light. According to wave theory of light, the light is a form of energy which travels through a medium in the form of transverse wave motion. The speed of light in a medium depends upon the nature of medium.
Newton’ s Corpuscular Theory
Light consists of very small invisible elastic particles which travel in vacuum with a speed of 3 x 10 8 m / s.
The theory could explain reflection and refraction. The size of corpuscular of different colours of light are different.
It could not explain interference, diffraction, polarisation. photoelectric effect and Compton effect. The theory failed as it could not explain why light travels faster in a rarer medium than in a denser medium.
Wavefront
A wavefront is defined as the continuous locus of all the particles of a medium, which are vibrating in the same phase.
These are three types( i) Spherical wavefront( ii) Cylindrical wavefront( iii) Plane wavefront