Derive the relation, μ = sin A + δ m 2 sin A 2 (symbols have their usual meanings) and show that i = A + δ m 2 , r = A 2 , for minimum angle fo deviation.

In the given diagram, O P is the incidence ray, which is making the angle i 1 with normal, and Q R is the angle of emergence, which is represented by i 2 . A is the prism angle and μ is the refractive index of the prism. Now, we know that, A = Prism angle, δ = Angle of deviation, i 1 = Angle of incidence, i 2 = Angle of emergent. In the case of minimum deviation, ∠ r 1 = ∠ r 2 = ∠ r A = ∠ r 1 + ∠ r 2 So, A = ∠ r = ∠ r = ∠ 2 r ∠ r = A 2 Now, again A + δ = i 1 + i 2 ( ∵ In the case of minimum deviation i 1 = i 2 = i and δ = δ m ) So, A + δ m = i + i = 2 i Now, i = A + δ m 2 Now, from snell's rule: μ = sin i sin r μ = sin A + δ m 2 sin A 2

E M B I B E

ISC Physics Class 12, Part-2>Chapter 4 - Refraction and Dispersion of Light through a Prism>QUESTIONS>Q 6

MEDIUM

12th ICSE

IMPORTANT

Earn 100

Draw ray diagram to illustrate formation of primary rainbow (using single water drop only and a single incident-ray, to show clearly refraction and total internal reflection, use at least four arrows).

Important Questions on Refraction and Dispersion of Light through a Prism

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 4 - Refraction and Dispersion of Light through a Prism>QUESTIONS>Q 1

A ray of light passes through a prism of angle

A

and emerges out at an angle of emergence

e

. Show that

i + e = A + δ

and when angle of incidence (i) is equal to angle of emergence, show that deviation produced is minimum.

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 4 - Refraction and Dispersion of Light through a Prism>QUESTIONS>Q 2

What is minimum angle of deviation? Draw graph between angle of incidence and deviation produced in the path of incident ray passing through a prism. Why

(i - δ)

curve has two arms?

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 4 - Refraction and Dispersion of Light through a Prism>QUESTIONS>Q 3

Derive the relation, $μ = \frac{\sin (\frac{A + δ_{m}}{2})}{(\sin \frac{A}{2})}$ (symbols have their usual meanings) and show that $i = \frac{A + δ_{m}}{2}, r = \frac{A}{2}$ , for minimum angle fo deviation.

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 4 - Refraction and Dispersion of Light through a Prism>QUESTIONS>Q 5

Define angular dispersion and dispersive power of an optical medium. Explain why deviation is maximum for violet colour and minimum for red colour also explain the dependence of deviation on the refractive index.

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 4 - Refraction and Dispersion of Light through a Prism>QUESTIONS>Q 1

A ray of light is incident on a