Let A, B, C be the glass of the prism. Suppose BC is the base and AB and AC are its two refracting surfaces. From the above figure, we can say that OP is the incident. The ray traveling through the rarer medium and than the refractive index of the prism is the incident ray. As the ray PQ strikes the surface of the and it is called as the refracted ray. OR is the emergent ray which comes out.
When the ray light enters the glass, it bends towards normal and when ray comes out, it bends away from the normal. Now the angle between the emergent ray and incident ray is the angle of deviation. For a single refracting surface, δ = i – r
In this case, δ = (i1 + i2) – (r1 + r2)
δ = i1 + i2 – A, A is the angle between the prism between two lateral surfaces.
We know that ∠A and ∠Q is 180º and Angle of the prism of (A) is: r1 + r2
r1 is the angle of refraction inside the prism and r2 is the angle of refraction outside it. For an angle of minimum deviation, δ is minimum and i1 = i2 = i
δmin = 2i – A
For small A, δ = (µ – 1) A
Minimum Angle of Deviation for a Prism: At the minimum deviation, Dm the refracted ray inside the prism becomes parallel to its base, i.e. i = e ⇒ r1 = r2 = r, then r = A/2 and Dm = 2i – A, where i is the angle of emergence, r1 and r2 are the angles of refraction and A is the angle of the prism.
Prism Formula
The refractive index of the material of prism:
Angular Dispersion: The angle subtended between the direction of emergent violet and red rays of light from a prism is called angular dispersion.
Angular dispersion
(θ) δ_{v} – δ_{R} = (μ_{v} – μ_{R})A
where δ_{v} and δ_{R} are angle of deviation.
Dispersive Power
W = θ/δ_{Y} = (μ_{v} – μ _{R}) / (μ_{Y} – 1)
where μ_{Y} = (μ _{v} + μ _{R} ) / 2, is mean refractive index.
158 videos453 docs185 tests

1. What is a prism? 
2. How does a prism disperse light? 
3. What is refraction of light through a prism? 
4. How does a prism refract light? 
5. What is the relationship between dispersion and a prism? 
158 videos453 docs185 tests


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