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Question
A wedge shaped air film having angle 40 seconds is illuminated by monochromatic light. Fringes are observed vertically through a microscope. The distance between 10 consecutive dark fringes is 1.2 cm. find the wavelength of monochromatic light used.
Solution
Given:
Θ = 40 seconds = `40 / 3600` degrees
`= 40 / 3600 xx ᴨ / 180 "radians," β = 0.12 cm`
Formula:
Spacing between the consecutive bright fringes is, β = `λ / (2θ)` (for air film)
The wavelength is, λ = 2β × θ
`Λ = 2 xx 0.12 xx 40 xx ᴨ / 3600 xx 180`
`= 46.54 xx 10^-8 cm`
`λ = 4654 A^0 `
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