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Q. State Huygen's principle. In the light of Huygen's principle, explain the refraction of light.

There are two principles of Huygen:

1. Every Point on the given wave front (called theprimary wave front) acts as a source of new disturbances,calledsecondary wavelets,which travel in all directions with the velocity of light.
2. A surface touching these wavelets tangentially in the forward direction at any instant gives the new wave front at that instant.This is called theSecondary wave front.​

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Refraction of light