Question

Explain Huygens’s principle of secondary wavelets.

Answer 1

- Hint: Huygens’s principle of secondary wavelets explains the properties of waves by construction of imaginary wave fronts and secondary wavelets emanating from them.

Complete step-by-step solution -

Huygens’s principle of secondary wavelets is one of the first theories that propagate the theory that light is a wave. However, when Huygens came out with this principle, he was largely ignored.
Huygens’s principle of secondary wavelets explains the properties of waves by construction of imaginary wave fronts and secondary wavelets emanating from them.
It states that “every point on the wave front of a wave is a source of smaller secondary spherical wavelets that move out in the forward direction from the wave front at the speed of the wave. This forms a new wave front which is a tangential surface to all these secondary wavelets”.
What this essentially means is that during the propagation of a wave, we can imagine a wave front which is made up of adding up all the tangential surfaces of the wave. From every point on this wave front, smaller secondary spherical wavelets emanate in the forward direction at the speed of the wave, thus giving rise to a subsequent wave front. This is responsible for the propagation of the wave.
This principle is able to explain all properties of a wave very successfully.

Note: Students must not memorize the statement of the principle since it can be a bit confusing and lead to mistakes. Instead, they should understand the explanation of the principle fully, and try to write the statement in their own words from their understanding of the principle.