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| Numerical - 22 |
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| 22. Red light of l = 650 nm from a distant source falls on a slit of 0.5 mm width. What is the distance between the two dark bands on each side of the central bright band of diffraction pattern observed on screen placed 1.8 m from the slit? |
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| Suggested solution: |
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| Figure shows the set up. O is the central bright fringe. D1 and D2 are the first dark fringe on either side of central maxima. Obviously |
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| Given |
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| = 6.5 x 10-7m: D = 1.8m, d = 5 x 10m |
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| The distance between D1 and Dl1 = 2x = 4.68mm |
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