Wave Optics - Huygen’s Principle
Description:
A source of light emits waves in all directions. All these waves travel in the medium with same speed i.e. waves in all direction travel the same amount of distance in a given time ’t’. Points in the same phase form a wavefront, these points act as a secondary source of light and each of them forms their own wavelet. At any given point the common tangential surface on these wavelets in forward direction forms a new wavefront and it results in the propagation of wavefront, in turn taking the light from the source to the observer. When this wavefront reaches the observer, the source of light is visible to the observer. This phenomenon of formation and propagation of wavefront was given by Huygens.
Main Observations by Huygens were -
Every point on a wavefront vibrates in same phase and with same frequency.
Every point on a wavefront acts like a secondary source and sends out a spherical wave, called a secondary wave.
A Wavefront moves in space with the velocity of wave in that medium.