A B and C D are surfaces of two slabs Fig. 13 . 75 . The medium between the slabs has refractive index 2. R.I. of the slabs are 2 and 3 respectively. Find the minimum angle of incidence at Q, so that the ray is totally reflected by both slabs.

Let θ be the angle of incidence at face AB, then for total internal reflection at face AB. sin θ > C 1 = μ 1 μ 2 = 2 2 ⇒ sin θ > 1 2 o r sin θ > sin 45 ° ⇒ θ > 45 ° For total internal reflection at face CD, sin θ > C 2 = μ 3 μ 2 = 3 2 ⇒ sin θ > 3 2 or sin θ > sin 60 ° o r θ > 60 ° Therefore, for total internal reflection at both the surfaces, θ m i n = 60 °

EASY

12th West Bengal Board

IMPORTANT

Earn 100

A ray of light is incident normally at the face $A B$ of a right-angled prism $A B C$ [Fig] of $(μ = 1.50)$ . What is the largest value of the angle $∠ A C B$ for which the ray is totally reflected at the surface $A C$ ?

Important Questions on Refraction of Light

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 20

The refracting angle of a prism is

90 °

; If

α

is the angle of minimum deviation and

β

the angle of deviation of a ray which enters at grazing incidence, then show that

α = \sin^{2} β

and

\cos α = μ \cos β,

where

μ

is the r . i of the prism.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 21

The refractive of the material of a prism of refracting angle

45 °

is 1.6 for a certain monochromatic ray. What should be the minimum angle of incidence of this ray on the prism so that no total internal reflection takes place as the ray comes out of the prism?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 22

A parallel beam of light falls normally on the first face of a prism of small angle.The portion of the beam which is refracted at the second surface is deviated through an angle of

6 ° 30^{'}

and the portion which is reflected at the second surface and emerges again at the first surface makes an angle of

1 ° 15^{'}

With the direction of the incident beam. Calculate the angle of the prism and the refractive index of glass.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 23

A ray of light within a glass slab immersed in water has critical angle

30 ° .

If the slab is immersed in another medium of r.i.

\sqrt{2}

, what will be the critical angle?

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 24

A ray of light is incident at an angle of

60 °

on one face of prism which has an angle of

30 ° .

The ray emerging out of the prism makes an angle of

30 °

with the incident ray show that the emergent ray is perpendicular to the face through which it emerges and calculate the refractive
index of the material of the lens.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 25

Light is incident at an angle

α

on one planer end of a transparent cylindrical rod of refractive index n. Determine the least value of

n

so that the light entering the rod does not emerge from the curved surface of rod irrespective of the value of

α

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 26

A B and C D are surfaces of two slabs Fig.

13.75

. The medium between the slabs has refractive index 2. R.I. of the slabs are

\sqrt{2}

and

\sqrt{3}

respectively. Find the minimum angle of incidence at Q, so that the ray is totally reflected by both slabs.

HARD

12th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART 2 : CLASS 12>Chapter 13 - Refraction of Light>EXERCISE 13>Q 27

Light enters a prism of angle A at a grazing incidence to emerge at angle $θ$ with the normal. Show that the refractive index of the material of the prism is given by

$μ = {[1 + {(\frac{\cos A + \sin θ}{\sin A})}^{2}]}^{\frac{1}{2}}$

A ray of light is incident normally at the face AB of a right-angled prism ABC [Fig] of μ=1.50. What is the largest value of the angle ∠ACB for which the ray is totally reflected at the surface AC?

Important Questions on Refraction of Light

Learn and Prepare for any exam you want !

A ray of light is incident normally at the face $A B$ of a right-angled prism $A B C$ [Fig] of $(μ = 1.50)$ . What is the largest value of the angle $∠ A C B$ for which the ray is totally reflected at the surface $A C$ ?