Question

What is wavefront? Describe Huygen's theory of secondary wavelets.

Answer 1

A wavefront is a surface over which an optical wave has a constant phase. For example, a wavefront could be the surface over which the wave has a maximum (the crest of a water wave, for example) or a minimum (the trough of the same wave) value.

Huygens wave theory describes about the wave nature of nature of wave propagation. When applied to the propagation of light waves, this principle states that:

"Every point on a wave-front may be considered a source of secondary spherical wavelets which spread out in the forward direction at the speed of light. The new wave-front is the tangential surface to all of these secondary wavelets."