Optics

Total No. of Questions: 30 Total Marks: 120

SECTION 1: MCQ
Q1 Consider a ray light passing through a rectangular glass slab. Let the emergent ray shift laterally by (4 Marks)
a distance x.The shift x depends on
A. angle of incidence
B. refractive index of the material of the slab
C. width of the slab
D. all the above

Q2 Which of the following is used in optical fibres? (4 Marks)

A. Total internal reflection
B. Scattering
C. Diffraction
D. Refraction

Q3 Choose the correct answer from the alternatives given. (4 Marks)

The refractive index and permeability of a medium are 1.5 and 5 × 10−7 H m−1 respectively. The
relative permittivity of the medium nearly
A. 25
B. 15
C. 10
D. 6

Q4 For total internal reflection, rays of light must go from: (4 Marks)

A. Rarer to denser medium
B. Rarer to rarer medium
C. Denser to rarer medium
D. Denser to denser medium

Q5 A ray of light is incident on a transparent glass slab refractive index 1.62. The reflected and the (4 Marks)
refracted rays are mutually perpendicular. The angle of incident is
A. 58.3o
B. 50o
C. 35o
D. 30o

Q6 Rectilinear motion of light in a medium is caused due to: (4 Marks)

A. high frequency
B. short wavelength
C. velocity of light
D. uniform refractive index of the medium

Q7 The speed of light in a vacuum is 3 × 108 m/s. If refractive index of glass is 1.5, the time taken by (4 Marks)
the light to travel 400 m in glass in microsecond is
A. 4.3
B. 8
C. 2
D. 3

1/6
Q8 The speed of light in two media I and II are 2.2 × 108 m/s and 2.4 × 108 m/s respectively. The (4 Marks)
critical angle for light refracting from I to II medium will be
−1
A. sin ( 12 11
) ​

−1 11
B. sin ( 12 )​

C. sin−1 ( 12
24
​ )
D. sin−1 ( 12
21
) ​

Q9 Light is incident from a medium into the air at two possible angles of incidence (a) 20o and (2) 40o . (4 Marks)
In the medium, the light travels 3 cm in 0.2 ns, the ray will:
A. Suffer total internal reflection in both cases
B. Suffer total internal reflection in case 2 only
C. Have 100% transmission is case 1
D. Have partial reflection and partial transmission in case 2

Q10 A beam of white light is incident on glass air interface from glass to air such that green light just (4 Marks)
suffers total internet reflection. The colors of the light which will come out to air are
A. Violet, Indigo, Blue
B. All colors except green
C. Yellow, Orange, Red
D. White light

Q11 A ray of light incident on a transparent block at an angle of incidence 60, If refractive index of (4 Marks)
block is 3 then the angle of deviation of the refracted ray is
​

A. 1500
B. 250
C. 300
D. 450

Q12 If the gas is lighter than air, sound waves are refracted (4 Marks)
A. away from the normal
B. towards the normal
C. total internal reflection
D. not sufficient data

Q13 An object 2.4 m in front of a lens from a sharp image on a film 12 cm behind the lens. A glass plate (4 Marks)
1cm behind the lens. A glass plate 1cm thick, of refractive index 1.50 is interposed between leans
and film with its plane force parallel to film. At what distance (from lens) should object shifted to be
sharp be in sharp focus on film

A. 7.2m
B. 2.4m
C. 3.2m
D. 5.6m

2/6
Q14 A stationary swimmer S, inside a liquid of refractive index μ1 is at a disance d from a fixed point P
​
(4 Marks)
inside the liquid. A rectangular block of width t and refractive index μ 2 (μ 2 < μ 1 ) is now placed
​ ​ ​

between S and P. A will observe P to be at a distance of :

d − t( + 1)
μ1
A.
​

μ2 ​

B. d − t ( 1 + )
μ2 ​

μ1
​

C. d + t ( 1 − )
μ2 ​

μ1 ​

D. d + t ( − 1)
μ2 ​

μ1 ​

Q15 A water film is formed on a glass-block. A light ray is incident on water film from air at an angle of (4 Marks)
60∘ with the normal. The angle of incidence on glass slab is
4
(μ g = 1.5, μ w = )
3
​ ​ ​

sin−1 ( )
3 3 ​

A.
8
​

1
B. sin ( )
−1
3
​

C. sin−1 ( )
4 3 ​

9
​

sin−1 ( )
9 3
D.
​

16
​

Q16 What is the angle of the prism for which there will be no emergent ray from the prism if C is the (4 Marks)
critical angle ?
A. 2C
B. less than 2C
C. more than 2C
D. None of these

Q17 8 8 (4 Marks)
The speed of light in media M1 and M2 are 1.5 × 10 m/s and 2.0 × 10 m/s respectively.
​ ​

A ray of light enters from medium M1 to M2 at an incidence angle i. If the ray suffers total
​ ​

internal reflection, the value of i is

A. Equal to sin−1 (2/3)
B. Equal to or less than sin−1 (3/5)
C. Equal to or greater than sin−1 (3/4)
D. Less than sin−1 (2/3)

Q18 The refractive indices of four substances W, X, Y, Z are 1.20, 1.77, 1.36, 1.50 respectively. (4 Marks)
When light passes from air into these materials, it refracts maximum in
A. W
B. X
C. Y
D. Z

3/6
Q19 A plano-convex lens when silvered on the plane side behaves like a concave mirror of focal length (4 Marks)
30 cm. However when silvered on the convex side, it behaves like a concave mirror of focal length
10 cm. The refractive index of its material is
A. 1.5
B. 2.0
C. 2.5
D. 3.0

Q20 A beaker of height '3h' has a radius 'h'. A thin rod of height 'h' is placed to the wall of the beaker. A (4 Marks)
person can see the top end of the rod from the opposite edge of the beaker through a pin hole. When
the beaker is filled with a liquid up to a height '2h', the person can see the bottom end of the rod. The
refractive index of the liquid is :
3
A.
2
​

B.
3 ​

2
​

5
C.
2
​

5
D.
2
​ ​

Q21 A plane mirror is held at a height h above the bottom of an empty beaker. The beaker is now filled (4 Marks)
with water up to depth d. The general expression for the distance from a scratch at the bottom of the
beaker to its image in terms of h and the depth d of water in the beaker is :

2h − d ( )
μ
A.
μ−1
​

d μ−1
B. 2h − ( )
2
​ ​

μ
μ−1
C. 2h − d ( ) ​

μ
2μ − 1
D. 2h − d ( )
μ
​

Q22 A beaker contains water up to a height h1 and kerosene of height h2 above water so that the total ​ ​
(4 Marks)
height of (water + kerosene) is (h1 + h2 ). Refractive index of water is μ1 and that of
​ ​ ​

kerosene is μ2 . The apparent shift in the position of the bottom of the beaker when viewed from
​

above is :
1 1
A. (1 + ) h1 − ( 1 + ) h2 ​ ​ ​ ​

μ1 μ2 ​ ​

1 1
B. ( 1 − ) h1 + ( 1 − ) h2 ​ ​ ​ ​

μ1 μ2 ​ ​

1 1
C. ( 1 + ) h2 − ( 1 + ) h1 ​ ​ ​ ​

μ1 μ2 ​ ​

1 1
D. ( 1 − ) h2 + ( 1 − ) h1 ​ ​ ​ ​

μ1 μ2 ​ ​

4/6
Q23 The refractive index of a certain glass is 1.5 for light where wavelength in vacuum is 6000Ao V (4 Marks)
The wavelength of this light when it passes through the glass is ___________.
A. 4000Ao
B. 6000Ao
C. 9000Ao
D. 15000Ao

Q24 A light wave enters from air into a medium of refractive index 1.5. The speed of light in the medium (4 Marks)
will be ____________.
A. 1 × 108 m/s.
B. 2 × 108 m/s.
C. 3 × 108 m/s.
D. 4 × 108 m/s.

8
Q25 Light travels in two media A and B with speeds 1.8 × 10 ms−1 and 2.4 × 108 ms−1 respectively. (4 Marks)
Then the critical angle between them is
2
A. sin−1 ( )
3
​

3
B. tan−1 ( )
4
​

2
C. tan−1 ( )
3
​

3
D. sin−1 ( )
4
​

Q26 3 (4 Marks)
A ray of light is travelling from air into a medium in which its velocity is reduced to of its velocity
4
​

in air. If it is incident at a very small angle on the surface of separation, and if i and r are the angles
of incidence and reflection respectively, then the deviation of the ray is given by?
4
A. δ = i − sin−1 ( sin i)
3
​

i
B. δ =
2
​

i
C. δ =
4
​

D. δ = 2r

Q27 (4 Marks)
The refractive index of a prism is 2. This prism can have a maximum refracting angle of
A. 600
B. C
C. 2C
D. Slightly less than 1800

Q28 Light passes through a glass plate of thickness 'd' and refractive index ′ μ ′ . For small angle of (4 Marks)
incidence 'i', the lateral displacement is
A. id
B. id(μ - 1)
id(μ − 1)
C.
μ
​

idμ
D.
μ−1
​

5/6
Q29 If any two media are optically exactly the same then; when light passes from one medium to another (4 Marks)
then:
A. No bending occurs
B. Sometimes it can bend
C. Compete bending occurs
D. None

Q30 If refractive index of a slab varies as m = 1 + x2 is measured from one end, then optical path (4 Marks)
length of a slab of thickness 1 m is
A. (4/3) m
B. (3/4) m
C. 1 m
D. None of these

6/6