The Huygen's construction of spherical wavefront in simple and easy way !!!

Here we come to know about the Huygen's construction of spherical wavefront.

So let's come to know,

i) The spherical wavefront is formed when the source of light is at the finite distance from the point of observation.

ii) So let's take 'S' be the point source of light in the air.

The point PQR represents spherical wavefront at any instant. 

The wavefront PQR is act as a primary wave, which is propagated through the air.

iii) So according to the Huygens principle, the all points on the PQR will act as a secondary source of light and sending out secondary wavelets with the same velocity 'c' in the air.

iv) To find out new wavefront at a later instant 't',

So for our clear understanding lets draw the hemisphere with the points P, Q, R....as centres and 'ct' as radius in the forward direction.

v) The surface tangential to all such hemisphere is an envelope at that instant 't'.

Such a surface is passing through the points P1Q1R1....so on the hemispheres and touching to all the hemispheres.

This surface is the new wavefront at that instant 't'.

vi) SPN1, SQN2, SRN3 these are the wave normal at points P, Q, R respectively.

vii) These wave normal show the direction of propagation of the spherical wavefront.

viii) The new wavefront P1Q1R1 is parallel to the points P, Q, R at every instant.

THE END

Thank you...!!!