Question

Light of wavelength lambda in air enters a medium of refractive index mu. Two points in this medium, lying along the path of this light, are at a distance of x apartThe phase difference between these point is

Answer 1

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λ is the wavelength of light in air.

Let t be the distance between points S and A.

Optical path length travelled by light via SB =μ(t+x)

Optical path length travelled by light via SA =μt

Path difference between points A and B Δx=SB−SA=μx

Now phase difference, ϕ=Δx×

λ

2π

Hence, ϕ=μ(

λ

2π

)x

Answer 2

Answer:

λ is the wavelength of light in air.

Let t be the distance between points S and A.

Optical path length travelled by light via SB =μ(t+x)

Optical path length travelled by light via SA =μt

Path difference between points A and B Δx=SB−SA=μx

Now phase difference, ϕ=Δx×

λ

2π

Hence, ϕ=μ(

λ

2π

)x