# A wedge shaped air film having angle 40 seconds is illuminated by monochromatic light. Fringes are observed vertically through a microscope. - Applied Physics 2

Numerical

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

Concept: Wedge Shaped Film(Angle of Wedge and Thickness Measurement)
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