In Young's double-slit experiment, the two slits which are separated by 1.2 mm are illuminated with a monochromatic light of wavelength 6000 A ∘ . The interference pattern is observed on a screen placed at a distance of 1 m from the slits. Find the number of bright fringes formed over 1 cm width on the screen.

Question

In Young's double-slit experiment, the two slits which are separated by 1.2 mm are illuminated with a monochromatic light of wavelength 6000 A ∘ . The interference pattern is observed on a screen placed at a distance of 1 m from the slits. Find the number of bright fringes formed over 1 cm width on the screen., 25, 12, 15, 20

MARKS App · Accepted Answer

Given: d = 1.2 mm , λ = 6000 Å = 6 × 10 - 7 m , D = 1 m , x = 1 cm = 1 × 10 - 2 m For n t h bright fringe, x = n λ D d ∴ 1 × 10 - 2 = n × 6 × 10 - 7 × 1 1.2 × 10 - 3 ∴ n = 1.2 × 10 - 5 6 × 10 - 7 = 0.2 × 10 2 = 20 There are 20 bright fringes formed over 1 cm width on the screen.

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