In Young’s double-slit experiment, fringe width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3 without disturbing geometry, the new fringe width will be:
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In Young’s double-slit experiment, fringe width is found to be 0.4 mm. If the whole apparatus is immersed in water of refractive index 4/3 without disturbing geometry, the new fringe width will be:

G1 Physics · Accepted Answer

Step 1: In water λ_w = λ_air/μ. Step 2: At unchanged D and d, β_w = β_air/μ. Step 3: β_w = 0.4/(4/3) = 0.30 mm. Final answer: (A) 0.30 mm.