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A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. What is the distance between the first dark fringe on either side of the central bright fringe? |
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Answer» Solution :For FIRST MINIMUM (n = 1) on EITHER SIDE of central maximum. `sin theta = (lambda)/(a)` Where a is width of the slit Since `theta` is very small. `(sin theta approx theta)` `theta = (lambda)/(a)` `sin theta approx theta = (x)/(2D)` Where, x is distance of first dark fringe from central maximum. D is distance between slit and screen. From equation (1) and (2) `(x)/(2D) = (lambda)/(a)` `x=(2Dlamda)/(a)=(2xx2xx600xx10^(-9))/(1xx10^(-3))` `=2400 xx 10^(-6) = 2.4 xx 10^(-3) m` x = 2.4 mm |
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