WHAT IS HUYGINS PRINCIPLE

Huygins principle states that every point on a wave front is a source of wavelets,which spread fore ward at the same speed.

The principle that any point on a wave front of light may be regarded as the source of secondary waves and that the surface that is tangent to the secondary waves can be used to determine the future position of the wave front.

The first person to explain how wave theory can also account for the laws of geometric optics was Christiaan Huygens in 1670. At the time, of course, nobody took the slightest notice of him. His work was later rediscovered after the eventual triumph of wave theory. Huygens had a very important insight into the nature of wave propagation which is nowadays called Huygens` principle. 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. According to Huygens` principle, a plane light wave propagates though free space at the speed of light. The light rays associated with this wave-front propagate in straight-lines. It is also fairly straightforward to account for the laws of reflection and refraction using Huygens` principle.