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| 1. |
What is the effect on the interference fringes in a Young.s double-slit experimental due to each of the following operations : The source slit is moved closer to the double-slit plane. |
| Answer» SOLUTION :Let s be the size of the source and S its distance from the plane of the two SLITS. For interference fringes to be seen, the condition `s"/"S lt lambda"/"d` should be SATISFIED, otherwise, interference patterns produced by different parts of the source overlap and no fringes are seen. Thus, as S DECREASES (i.e., the source slit is brought closer), the interference pattern gets LESS and less sharp, and when the source is brought too close for this condition to be valid, the fringes disappear. Till this happens, the fringe separation remains fixed. | |