In a Young double-slit experiment, the fringe width in air is 2.4 μm. The entire experiment is then carried out in a transparent medium of refractive index 1.2, while the slit separation and screen distance remain unchanged. What is the new fringe width?
Options

Question

In a Young double-slit experiment, the fringe width in air is 2.4 μm. The entire experiment is then carried out in a transparent medium of refractive index 1.2, while the slit separation and screen distance remain unchanged. What is the new fringe width?

Options

G1 Physics · Accepted Answer

In a medium of refractive index μ, the wavelength becomes λ' = λ ÷ μ. Since fringe width is β = λD ÷ d, with D and d unchanged, β' = β ÷ μ. Therefore, β' = 2.4 ÷ 1.2 = 2.0 μm. Correct option: B.