Huygens Principle

 Huygens Principle :

       When a luminous point source of light creates a disturbance, the energy of the disturbance in propagated through a transparent medium in the form of waves. To explain how this propagation of light waves takes place, Huygens proposed certain principle which is as follows :

(1)        Every point on a wave-front behaves as if it is a secondary source of light sending secondary waves as possible  directions.

(2)        The new secondary wavelets are more effective in the forward directions. (i.e. directions of propagation of wave-front )

(3)            The resultant wave-front at any positions is given by the tangent to all the secondary wavelets at that instant.