Given μ g a = 3 2 and μ w a = 4 3 . Find μ g w and the corresponding critical angle.

Given in the question, μ g a = 3 2 , μ w a = 4 3 We can write, μ g = w μ g a × μ a w or, μ g = w 3 2 × 3 4 or, μ g = w 9 8 = 1 . 11 Now, we know that the critical angle is the angle of incidence, for which the angle of refraction is 90 . So, we can write, μ g = w 1 sin C = 9 8 or, C = sin - 1 0 . 88

Radius of each surface of a convex lens is 20 cm and the refractive index of the material of the lens is 3 2 . If it is vertically divided into two equal halves, find focal length.

As we know that lens maker formula is, 1 f = μ - 1 × 1 r 1 - 1 r 2 When the lens is divided vertically and it is made a plano-convex lens, so r 2 will become infinity. For the given plano-convex lens, r 1 = 20 cm and r 2 = ∞ and refractive index, μ = 3 2 So, putting all these values, 1 f = 3 2 - 1 × 1 20 - 1 ∞ On solving, we get 1 f = 1 2 × 1 20 or, f = 40 cm So, the focal length for the plano-convex lens will be 40 cm .

HARD

12th Odisha Board

IMPORTANT

Earn 100

What is transverse magnification? Derive an expression, with the help of ray-diagrams, for magnification for a different types of images in convex and concave lenses.

Important Questions on Refraction, Dispersion and Lens

HARD

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 8

What is dispersion? Define dispersive power, angular dispersion and establish a relation between them.

EASY

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 1

Given

{}_{a}{μ_{g}} = \frac{3}{2}

and

2 -

. Find

{}_{w}{μ_{g}}

and the corresponding critical angle.

MEDIUM

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 2

A prism of refractive index

\sqrt{2}

has a refracting angle of

60 °

. At what angle a ray must be incident on it, so that it suffers a minimum deviation ?

MEDIUM

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 3

A ray of monochromatic light is incident on the refracting face of a Prism angle

75 °

. It passes through the prism and is incident on the other face at the critical angle. If the refractive index of the prism is

\sqrt{2}

, what is the angle of incidence on the first face of the Prism ?

HARD

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 4

A ray of light is incident at an angle of

60 °

on one face of a Prism which has an angle of

30 °

. The ray emerging out of the Prism makes an angle

30 °

with the incident ray. Show that the emergent ray is perpendicular to the face through which it emerges and calculates the refractive index of the prism.

MEDIUM

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 5

The Refractive index of crown glass for red, yellow, violet colours are

1.5140, 1.5170

and

1.5318

respectively and for flint glass are

1.6434, 1.6499

and

1.6852

respectively. Find the dispersive power of the crown and flint glass.

EASY

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 6

Radius of each surface of a convex lens is

20 cm

and the refractive index of the material of the lens is

\frac{3}{2}

. Calculate its focal length.

HARD

12th Odisha Board

IMPORTANT

Bureau's Higher Secondary Physics Class 12>Chapter 12 - Refraction, Dispersion and Lens>MODEL QUESTIONS>Q 6

Radius of each surface of a convex lens is

20 cm

and the refractive index of the material of the lens is

\frac{3}{2}

. If it is vertically divided into two
equal halves, find focal length.

What is transverse magnification? Derive an expression, with the help of ray-diagrams, for magnification for a different types of images in convex and concave lenses.

Important Questions on Refraction, Dispersion and Lens

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