# WHAT IS HYGENS PRINCIPLE

Gayatri Jayesh Bondriya
521 Points
8 years ago
Huygens�s principle
Huygens principle of wave propagation is a geometrical description used to determine the new position of a wave front at later time from its given position at any given instant of time. It is based on two principles
Each point on a given or primary wave front acts like a new source sending out disturbance in all directions and are known as secondary wavelets
The envelope or the tangential plane to these secondary wavelets consitutes the new wave front
To understand the propagation of wave on the basis of these postulates consider the figure given below

For simplicity we are considering the simple case of a plane wave
a) Let at time t=0,W1 be the wave front which spates those part of the medium which are undisturbed from those where wave has already reached
b) Each point on W1 acts as a source of secondary waves by sending out spherical wave of radius vt where v is the velocity of the wave
c) After some time t, the disturbance in the medium reaches all points within the region covered by all t these secondary waves. The boundary of this region is new wave front W2 and W2 is the surface tangent to all spheres and is known as forward envelope of these secondary wave fronts
d) The secondary wave fro pint A1 on W1 touches W2 at A2.The line connecting point A1 and A2 on wavelength W1 and W2 respectively is a ray of length vt.This is the reason why rays are perpendicular to the wave fronts
e) We can repeat this construction starting with W2 to get the next wave fronts W3 at some later time t2 and so on
We have explained Huygens construction using a place wave fronts but the construction is more general than our simple example .The wave fronts can have any shape and sped of waves can be different at different places and in different direction's

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KUNCHAM SAMPATH
402 Points
8 years ago
Huygens principle of wave propagation is a geometrical description used to determine the new position of a wave front at later time from its given position at any given instant of time