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In the Young's double slit experiment , a point source of lambda = 5000Å is placed slightly above the central axis as shown in the figure. (a) Find the nature and order of the interference at the point P. (b) Find the nature and order of the interference at O. (c)Where should we place a film of refractive index mu=1.5 and what should be its thickness so that maxima of zero order is obtained at O. |
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Answer» waves arriving at P is `Deltax = (y_1d)/(D_1) + (y_2d)/(D_2)` ` = ((1)(10))/10^3 + ((5)(10))/(2xx10^3)` ` = 3.5 xx 10^-2 mm = 0.035 mm` As, `Deltax = 70 LAMBDA` `:.` 70th order maxima is OBTAINED at P. (B) At O, `Deltax = (y_1d)/D_1 = 10^(-2) mm ` = 0.01 mm As `Delta x = 20 lambda` `:.` 20 th order maxima is obtained at O. (c) `(mu -1)t = 0.01 mm ` `:. t = (0.01)/(1.5 -1) = 0.02 mm = 20 mum ` Since, the pattern has to be shifted upwards, therefore, the film must be placed in front of `S_1` . |
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