A complete single-slit diffraction arrangement is immersed in a transparent medium of refractive index 1.5. The slit width and all geometrical distances remain unchanged. If the angular width of the central maximum in air is Θ, what is the angular width in the medium?
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Question

A complete single-slit diffraction arrangement is immersed in a transparent medium of refractive index 1.5. The slit width and all geometrical distances remain unchanged. If the angular width of the central maximum in air is Θ, what is the angular width in the medium?

Options

G1 Physics · Accepted Answer

The frequency of light does not change on entering the medium. Therefore the wavelength becomes λ' = λ ÷ μ. With μ = 1.5 = 3 ÷ 2, λ' = 2λ ÷ 3. Angular width is Θ = 2λ ÷ a. Hence, Θ' = 2λ' ÷ a = 2 ÷ 3 × Θ. Therefore, Θ' = 2Θ ÷ 3. Correct option: B.