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In a biprism, 21 fringes are distinctly seen on screen at a distance of 1 m, when the sources are 0.5 mm apart, what is the coherent length and coherent time of the set up .(lambda = 6000 Å): |
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Answer» `2 xx 10^(-14) sec` `therefore Delta_(max) = (x_(max).d)/(D)` For distinct FRINGES, `Delta_(max) = l_(coh)` Here `x_(max) = 10 beta` `l_(coh) = Delta_(max) = (10beta d)/(D)` `therefore l_(coh) = (10d)/(D) .(lambdaD)/(d) = 10 LAMBDA = 6mu m`. `T_(coh) = (l_(coh))/(C) = (6 xx 10^(-6))/(3 xx 10^(8)) = 2 xx 10^(-14)S`. |
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