Question

A beam of light consisting of two wavelengths 7000 Å and 5500 Å is used to obtain interference pattern in Young's double slit experiment. The distance between the slits is 2.5 mm and the distance between the plane of slits and the screen is 150 cm. The least distance from the central fringe, where the bright fringes due to both the wavelengths coincide, is n × 10^-5 m. The value of n is_____.

Answer 1

Correct answer is 462

Let n^th bright tringle of λ₁ match with m^th bright triangle of λ₂

Distance where bright fringe will match

Comments

Why only 7000A°, why not 5500A°

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Because of least distance- from central maxima