# A Parallel Beam of Light of Wavelength 5890 A0 is Incident on a Glass Plate Having Refractive Index 𝝁=𝟏.𝟓 Such that the Angle of Refraction in the Plate is 600. Calculate the Smallest Thickness - Applied Physics 2

Sum

A parallel beam of light of wavelength 5890 A0 is incident on a glass plate having refractive index 𝝁=𝟏.𝟓 such that the angle of refraction in the plate is 600. Calculate the smallest thickness of the glass plate which will appear dark by reflected light.

#### Solution

Given: - λ=5890 x 10-8 cm

𝜇=1.5

r=60O

To Find: - t=?
Formula: - 2 𝜇t cos r= n λ

The smallest thickness will be for n=1,

2×1.5×𝑡×cos60=1×5890×10−8

t=(5890xx10^-8)/(2xx1.5xx0.5)
𝒕=𝟑𝟗𝟐𝟔×𝟏𝟎−𝟖𝒄𝒎

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