Question

state "huygen's principle"?​

Answer 1

When applied to the propagation of light waves, this principle states that: Every point on a wave-front may be considered a source of secondary spherical wavelets which spread out in the forward direction at the speed of light. The new wave-front is the tangential surface to all of these secondary wavelets

Answer 2

$\Large\underline\mathfrak{Question}$

State Huygens principles?

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$\Large\bold\green\star\underline{\underline\textbf{Use of Huygen's Principle\:}}$

→ Huygen's principle is used to find the position of the given wavefront at any instant of time, provided its present location is known.

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$\Large\bold\star\underline{\underline\textbf{Huygen's Principle\:}}$

→ According to this principle

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• Every point on the given wavefront acts as a source of new disturbance, called secondary wavelets which travel in all directions. The velocity of secondary wavelets is same as that of primary wavelets and is equal to velocity of light.

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• A tangent to the secondary wavelets in the forward direction at any instant gives the position of secondary wavefront at that instant.

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• In a homogeneous medium, the wavefront is alwavs normal to the direction of propagation of waves. Consider a primary wave front AB and take points 1, 2, 3, 4,--------- etc. on this wavefront. The distance travelled by light in 't' seconds= c x t, where c is the velocity of light. Now taking each point 1, 2, 3, 4,..... as centres and radius equal to c x 1, draw spheres. These spheres are called secondary wavelets. Now draw a tangent or envelope A1B1 to these spheres. The surface A2B2 is the position of secondary wavefront after 't' seconds .

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