In a double-slit experiment, wavelength 400 nm gives angular width of the first minimum 0.2°. What will be its angular width when the apparatus is immersed in water? (μ_water = 4/3)
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In a double-slit experiment, wavelength 400 nm gives angular width of the first minimum 0.2°. What will be its angular width when the apparatus is immersed in water? (μ_water = 4/3)

G1 Physics · Accepted Answer

Step 1: Angular fringe scale θ ∝ λ/d. Step 2: In water wavelength becomes λ_w = λ_air/μ and slit separation is unchanged. Step 3: θ_w = θ_air/μ = 0.2°/(4/3) = 0.15°. Final answer: (A) 0.15°.