Question

What is the Huygens Principle?

Answer 1

See the explanation below.

Explanation:

If we know the shape and location of a wavefront at any instant `t` , we are able to determine the shape and location of the new wavefront at a later time `t+Deltat` with the help of Huygens principle. It consists of two parts :

• Every point of a wavefront may be considered as a source of secondary wavelets which spread out in forward direction with a speed equal to the speed of propagation of the wave.
• The new position of the wavefront after a certain interval of time can be found by constructing a surface that touches all secondary wavelets.
  This principle can be illustrated by the help of a figure shown below:

To determine the wavefront at `t+Deltat`, we draw secondary wavelets with centre at various points on first wavefront and radius will be `cDeltat` where `c` is the speed of propagation of wave.The new wavefront at time `t+Deltat` will be a tangent to all secondary wavelets as shown in above figure.

In the figure,On the left side is a plane wavefront and on right side is spherical wavefront .