In a double slit experiment, two slits are 1 mm apart and the screen is 1 m away. Monochromatic light of wavelength 500 nm is used. What should be the width of each slit for obtaining ten maxima of double-slit interference within the central maximum of single-slit pattern?
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Question

In a double slit experiment, two slits are 1 mm apart and the screen is 1 m away. Monochromatic light of wavelength 500 nm is used. What should be the width of each slit for obtaining ten maxima of double-slit interference within the central maximum of single-slit pattern?

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G1 Physics · Accepted Answer

Step 1: Central diffraction maximum width Y ≈ 2λD/a, with slit width a. Step 2: Interference fringe width β = λD/d. Step 3: Number across central diffraction maximum N ≈ Y/β = 2d/a. Step 4: Set N = 10 and d = 1 mm ⇒ a = 2d/10 = 0.2 mm. Final answer: (A) 0.2 mm.