QQuestion
A light is incident from air medium on another medium. If the refractive index of this medium is 1.5 and the wavelength of light in this medium is 4000 Å what is the wavelength of light in the air medium ? What is the velocity of the light in this medium? [3]
OR
As a result of refraction of light through an equilateral prism the angle of deviation becomes 40°. If the path of the ray through the prism is parallel to the base of the prism, determine the angle of incidence at the first surface of prism. [3]
✓Answer
Finding the wavelength:
μ = 1.5
λmedium = 4000 Å
λair = μ × λmedium
⇒ λair = 1.5 × 4000 = 6000 Å
Find the velocity:
μ = 1.5
vair = 3 × 108 m/s
vmedium = 3 × 108/1.5 = 2 × 108 m/s
OR
Angle of deviation (δ) = 40º
Angle of prism (A) = 60º
We know, δ = 2i−A
⇒ i = δ + A\over 2
⇒ i = 40º + 60º\over 2 = 50º
The angle of incidence at the first surface of the prism is 50°.
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