In a Young's double-slit experiment, the slit separation is d = 0.20 mm, the screen distance is D = 1.0 m, and light of wavelength lambda = 600 nm is used. What is the fringe width (fringe separation beta)?

Answer and explanation

Correct answer: C. 3.0 millimeters

  1. Step 1: Fringe width formula: beta = lambda D / d. Step 2. lambda = 600 x 10^-9 m, D = 1.0 m, d = 0.20 x 10^-3 m = 2.0 x 10^-4 m. Step 3. beta = (600 x 10^-9 1.0) / (2.0 x 10^-4) = 3.0 x 10^-3 m = 3.0 mm. Answer: 3.0 millimeters. Why not the others: 0.30 mm has a factor of 10 error; 1.2 mm results from d = 0.5 mm.

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