concept of wave front the basis of huygens

Question

Concept of wave front 

• The basis of Huygens wave theory of light is his principle concerning construction of wave front.
• When a disturbance from a light source travels into ether medium in all three dimensions, the particles of the medium at different distancesfrom the source will be vibrating in different phases.
• If we join all those particles which are in the same phase of Vibration, we get a surface which represents a wavefront.
• These wave fronts can be of different shapes depending on the size and shape of a light source and the distance from it.
• Now it is easy to imagine how rays are formed out of these wavefronts. 
• An imaginary line drawn normal to any wavefront represents the path along which light travels 
• This path is called light ray.