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Question
A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes in a Young’s double-slit experiment.
Find the distance of the third bright fringe on the screen from the central maximum for wavelength 650 nm.
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Solution
Here, d = 2 mm = 2 × 10-3 m, D = l.2 m, λ1 = 650 nm = 650 × 10−9 m, λ2 = 520 nm = 520 × 10−9 m
Distance of the third bright fringe from the central maximum for the wavelength 650 nm:
y3 = `(3λ_1D)/d`
= `(3(650 xx 10^-9)1.2)/(2 xx 10^-3)`
= 1.17 × 10-3 m
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