Sunlight strikes a piece of crown glass at an angle of incidence of 37.4o. Calculate the difference in the angle of refraction between a red (660 nm) and a blue (470 nm) ray within the glass. The index of refraction is n

The difference in angle of refraction between the red and blue light is 0.2°

Explanation:

Here is the complete question

Sunlight strikes a piece of crown glass at an angle of incidence of 37.4°. Calculate the difference in the angle of refraction between a red (660 nm) and a blue (470 nm) ray within the glass. The index of refraction is n=1.520 for red and n=1.531 for blue light.

Solution

From Snell's law refractive index n = sini/sinr where i = angle of incidence and r = angle of refraction.

Now for the red light n₁ = 1.520, i = 37.4° and r₁ = angle of refraction of red light

So, n₁ = sini/sinr₁

n₁sinr₁ = sini

sinr₁ = sini/n₁

r₁ = sin⁻¹(sini/n₁) = sin⁻¹(sin37.4°/1.52) = sin⁻¹(0.6074/1.52) = sin⁻¹(0.3996) = 23.55°

Now for the blue light n₂ = 1.531, i = 37.4° and r₂ = angle of refraction of blue light

So, n₂ = sini/sinr₂

n₂sinr₂ = sini

sinr₂ = sini/n₂

r₂ = sin⁻¹(sini/n₂) = sin⁻¹(sin37.4°/1.531) = sin⁻¹(0.6074/1.531) = sin⁻¹(0.3967) = 23.37°

So the difference in angle of refraction between the red and blue light is r₁ - r₂ = 23.55° - 23.37° = 0.18° ≅ 0.2°

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