7.
R
sin i
at
•
•
•
l
•
•
•
n
•
e
U
a
on
lu
•
G
c
=
ti
e
r
v1
v2
i = angle of incidence
r = angle of refraction
v 1 = velocity of light in medium first
v 2 = velocity of light in medium second
When a ray of light moves from an optically rarer medium to an optically denser
medium, the ray bends towards the normal. In this case, 1 < 2, and i > r.
When a ray of light moves from an optically denser medium to an optically rarer
medium, the ray bends away from the normal. In this case, 1 > 2, and i < r.
When a ray of light is incident normal to the interface between any two media,
the ray propagates undeviated from one medium to another. In this case, i = 0º.
Twinkling of stars, advanced sunrise and delayed sunset are large scale effects of
atmospheric refraction.
Advanced sunrise and delayed sunset increases duration of day by four minutes.
The phenomenon of spliting of light into its component colours is dispersion. The
band of coloured components of a light beam is called its spectrum.
When white light is dispersed into seven colours by a prism, red light bends the
least while violet light bends the most.
The beautiful phenomenon of the rainbow is a combination of different phenomena
- dispersion, refraction and reflection of light.
When a ray of light is incident on extremely small particles, the particles deflect
the light in different directions. This phenomenon is scattering of light.
Reddish orange colour of the sky at sunrise and sunset, blue colour of the sky
etc., are the effects of scattering of light.
In the visible range of light maximum scattering of blue light and the least scattering
of red light takes place.
As red light is scattered the least by atmosphere it can travel larger distance.
The wave length of blue light is smaller than the wave length of red light.
 or 1 2
t
s
• Refractive index () = sin r
So
p
•
e
a
•
of light.
The phenomenon of change in the direction of light when it passes from one
transparent medium to another is called refraction.
The extent of change in the direction of light ray is related to the refractive index
of the medium.
qu
h
• Reflection, refraction, scattering and dispersion are the natural phenomena
ni
C
Wonders of Light - Part II
•
•
•
•
•
SCIENCE & TECHNOLOGY - S.S.C.
103
MULTIPLE CHOICE QUESTIONS (MCQ's)
(Each question carries one mark)
MCQ's BASED ON PRACTICALS
Experiment : I. To trace the path of a ray of light passing through a rectangular glass slab
for different angles of incidence.
Measure the angle of incidence, angle of refraction, angle of emergence and interpret the
results.
R
A student performs the experiment on tracing the path of ray of light passing through a
rectangular glass slab for different angles of incidence. He/she measures angle of refraction
and angle of emergence for all observations. He/she finds that in all cases:
a angle of incidence is more than angle of refraction but nearly equal to angle of emergence.
b angle of incidence is less than angle of refraction but nearly equal to angle of emergence.
c angle of incidence is more than angle of emergence but nearly equal to angle of refraction.
d angle of incidence is less than angle of emergence but nearly equal to angle of refraction.
When a ray of light travels from air to glass and strikes the surface of separation at 90°
then it:
a bends towards normal
b bends away from normal
c passes unbent
d returns to air
When a ray of light is incident from a denser medium of refractive index 2, it goes in a
straight line. What should be the angle of incidence?
a just less than 30°
b just less than 40° c just less than 60°
d just less than 90°
A ray of light strikes the glass slab at an angle of 50°, What is the angle of incidence?
a 50°
c 140°
b 40°
d none of these
A glass slab is placed in the path of convergent light. The point of convergence of light :
a moves towards the slab
b moves away from slab
c remains at the same point
d undergoes lateral shift
Water in a swimming pool appears shallower than its depth due to :
a reflection of light
b refraction of light c scattering of light
d dispersion of light
Change in the direction of light due to change in medium is called :
a dispersion
c refraction
b scattering
d reflection
When a light ray moves from a denser medium to a rarer medium, the ray :
a bends away from the normal
b bends towards the normal
c propagates undeviated
d gets reflected
The apparent depth of an object placed in a denser medium and seen through a rarer
medium is :
a greater than the real depth
b less than the real depth
c equal to the real depth
d double than the real depth
When a light ray passes from a rarer medium to a denser medium :
a i>r
c i=r
b i<r
d  i  r
When a light ray is incident normal to the interface between any two media, the angle of
incidence is :
a 90º
c 45º
b 0º
d 180º
A ray of light incident normal to the interface travels :
a away from normal
c towards normal
b backward
d undeviated
Light enters from air to glass having refractive index 1.50. What is the speed of light in glass?
a 3 × 108 m/s
c 1.2 × 108 m/s
b 1.5 × 108 m/s
d 2 × 108 m/s
7.
8.
9.
10.
11.
12.
13.
ti
lu
So
6.
e
5.
qu
4.
ni
3.
U
2.
on
s
1.
Wonders of Light - Part II
104
Unique
MCQ's
MCQ's BASED ON CHAPTER
Moderate Level
6.
7.
8.
9.
10.
11.
R
s
qu
12.
on
5.
ti
4.
lu
3.
So
2.
Refraction occurs due to :
a change in velocity of light
b splitting of light
c deflection of light
d change in wave length of light
For a given pair of media if 'i' is the angle of incidence and 'r' is the angle of refraction
then, which of the following is a constant?
a sin i × sin r
c sin r / sin i
b sin i / sin r
d sin i + sin r
Which of the following has the highest refractive index?
a ruby
c diamond
b rock salt
d sapphire
Which of the following is the rarest medium?
a air
c water
b ice
d alcohol
The refractive index of water is :
a 1.44
c 1.31
b 1.36
d 1.003
The phenomenon of splitting of light into its component colours is called :
a refraction
c scattering
b reflection
d dispersion
The first scientist who used a glass prism to obtain the spectrum of light was :
a Dr. C.V. Raman
c Sir Issac Newton
b Hans Oersted
d George Ohm
By how much time is sunrise advanced or sunset delayed due to atmospheric refraction?
a 2 min.
c 6 min.
b 4 min.
d 8 min.
Which component of white light bends the most when it is dispersed into seven colours by
a prism?
a red
c yellow
b blue
d violet
The speed of light in vacuum is :
a 2.4 × 108 m/s.
c 3 × 108 m/s.
b 2 × 108 m/s.
d 1.8 × 108 m/s.
In which of the following does light travel faster?
a kerosene
c benzene
b alcohol
d ice
Recombination of the spectrum of sunlight results into :
a VIBGYOR
c blue light
b red light
d white light
e
1.
Suppose v1 is the velocity of light in medium 1 and v2 is the velocity of light in medium 2,
the refractive index of the second medium with respect to the first medium is given by :
v1
v2
v2
v1
c 2 1 =
b 1 2 =
d 1 2 =
v2
v1
v1
v2
Which of the following is an effect of scattering of light?
a spectrum
b rainbow
c blue colour of the sky
d twinkling of stars
Which of the following is not an effect of refraction of light?
a advanced sunrise
c twinkling of stars
b blue sky
d delayed sunset
The beautiful phenomenon of the rainbow is a combination of different phenomena a scattering, dispersion and refraction.
b dispersion, refraction and reflection.
c refraction, reflection and scattering.
d reflection, scattering and dispersion.
U
1.
ni
Elementary Level
a
2.
3.
4.
2
1 =
Wonders of Light - Part II
SCIENCE & TECHNOLOGY - S.S.C.
5.
6.
7.
Refractive index of warm air is :
a less than cool air
b more than cool air
c same as cool air
d changing continuously
The apparent position of a star in the sky is :
a far away from its actual position
b slightly lower than its actual position
c slightly higher than its actual position
d same as that of its actual position
Which component of sunlight is scattered the least by atmosphere?
a red light
c green light
b blue light
d violet light
Very fine particles in the atmosphere mainly scatter :
a white light
c orange light
b red light
d blue light
Stars appear twinkling at night due to :
a reflection of light
b refraction of light c dispersion of light
d scattering of light
Sky appears blue because :
a blue light does not get scattered
b blue light has longer wavelength
c blue light is scattered maximum
d blue light is scattered the least
Red light can travel larger distance because :
a it is scattered the most by the atmosphere b it is scattered the least by the atmosphere
c it travels with great speed
d it has short wavelength
10.
ti
11.
on
9.
s
R
8.
105
2.
If a light ray bends away from normal after refraction through a medium, which of the
following is correct?
a 1 < 2
c i>r
b 1 = 2
d 1 > 2
After refraction, if a light ray bends towards normal, which of the following is incorrect?
v1
c 1 < 2
b 1 > 2
d i>r
v2
Planets do not twinkle like stars because :
a they are point sources of light
b they are nearer to the earth as compared to stars
c they are far away from the earth as compared to stars
d the refractive index of atmosphere remains constant
By how much time does the duration of a day increase due to advanced sunrise and
delayed sunset?
a 2 min.
c 4 min.
b 8 min.
d 6 min.
Sky appears reddish orange at sunrise or sunset because :
a red and orange lights are scattered the most
b red and orange lights are scattered the least
c blue and violet lights are scattered the least
d blue and violet lights are scattered the most
Danger signals are red coloured because :
a red colour denotes danger
b red light is scattered the most
c red light can travel larger distance
d red light can travel only shorter distance
Who was the first Indian scientist to get the Nobel Prize?
a Sir Issac Newton
c Newlands
b Dr. C.V. Raman
d Andre Ampere
6.
7.
ni
qu
5.
U
4.
e
a =
3.
So
1.
lu
Complex Level
Wonders of Light - Part II
106
Unique
MCQ's
Mysterious Level
1.
The speed of light in a transparent medium is 1.2 × 10 8 m/s. What is the absolute refractive
index of the medium?
a 2.25
c 2.5
b 0.4
d 1.5

Hint : 12 =
2.
What is the speed of light in diamond, if absolute refractive index of diamond is 2.4 and
velocity of light in vacuum is 3 × 108 m/s?
a 2.2 × 108 m/s
c 1.25 × 108 m/s
b 2.5 × 108 m/s
d 3 × 108 m/s

Hint : 12 =
3.
If 12 =
s
R
v1
v2
on
v1
v2
4
and v 2 = 2.25 × 108 m/s, find v1
3
b 3 × 108 m/s
v1
v2
c 3.5 × 108 m/s
ti
a 2 × 108 m/s
d 1.5 × 108 m/s
Hint : 12 =
4.
The speed of light in water and glass is 2.2 × 10 8 m/s and 2 × 108 m/s respectively. What
is the refractive index of glass w.r.t. water?
a 9.9
c 0.11
b 0.909
d 1.1

Hint : 12 =
5.
If the refractive index of a medium is 2.5 and speed of light in air is 3 × 10 8 m/s, what is
the speed of light in the given medium?
a 3.2 × 108 m/s
c 1.2 × 108 m/s
b 2.5 × 108 m/s
d 1.8 × 108 m/s

Hint : 12 =
6.
What is the refractive index of the second medium w.r.t. the first medium, if light moves
through the first medium with a velocity 2 × 10 8 m/s, which changes to 1.25 × 108 m/s in
second medium?
a 1.6
c 1.5
b 1.67
d 1.47
So
lu

qu
e
v1
v2
U
ni
v1
v2
v1
v2

Hint : 12 =
7.
If the absolute refractive index of a medium is 1.25, what is the speed of light in this
medium?
a 2.5 × 108 m/s
c 1.25 × 108 m/s
b 2.4 × 108 m/s
d 3.4 × 108 m/s

Hint : 12 =
v1
v2
Wonders of Light - Part II
SCIENCE & TECHNOLOGY - S.S.C.
107
8.
The absolute refractive index of benzene is 3/2. Find the speed of light in benzene.
a 3 × 108 m/s
c 2 × 108 m/s
b 3.5 × 108 m/s
d 2.5 × 108 m/s

Hint : 12 =
9.
The speed of light in medium 1 and medium 2 is 2.4 × 10 8 m/s and 1.8 × 108 m/s respectively.
Find the refractive index of medium 1 w.r.t. medium 2.
a 1.3
c 0.13
b 0.75
d 7.5

Hint : 21 =
R
v1
v2
s
v2
v1
on
Answers
MCQ's BASED ON PRACTICAL SKILLS
a
b
b
2
7
12
-
c
c
d
3
8
13
Complex Level
U
Mysterious Level
-
a
b
5
10
-
b
a
- a
2
-
b
3
-
c
4
-
a
5
-
b
6
- d
7
-
c
8
-
a
9
-
d
10
-
c
11
- d
12
-
d
1
6
11
- d
- c
- b
2
7
-
c
a
3
8
-
b
d
4
9
-
b
b
5
10
-
a
c
1
- d
2
-
b
3
-
b
4
-
c
5
-
b
6
- c
7
-
b
1
- c
2
-
c
3
-
b
4
-
d
5
-
c
6
- a
7
-
b
8
-
c
9
-
b
ni
qu
Elementary Level
4
9
1
e
Moderate Level
So
MCQ's BASED ON CHAPTER
a
a
d
-
ti
-
lu
1
6
11

Wonders of Light - Part II