Light Reflection and Refraction

1. Observe the given figure.

What is the angle of reflection?

(a) 20 (b) 40
(c) 70 (b) 90 Given that the refractive index of air is 1.0 and
the refractive index of glass is 1.5, what is the
2. An object O is placed in front of a plane mirror angle of refraction?
as shown below. (a) 22.6 (b) 30.8
(c) 35.3 (d) 40.0

6. Which of the following correctly represents the

incident ray, the refracted ray and the emergent
ray in the given glass slab?

At which point is the image of the object

'O' formed?
(a) P (b) Q
(c) R (d) S

3. A ray of light travels from water to air as shown

below.
Incident Refracted Emergent
ray ray ray
(a) PQ QR RS
(b) PQ RS QR
(c) RS QR PQ
(d) RS PQ QR

7. A ray of light travels from water to air as shown

below.
Given that the refractive index of air is 1.0 and
the refractive index of water is 1.3, what is the
angle of incidence?
(a) 22.6 (b) 23.1
(c) 39.0 (d) 40.5

4. The radius of curvature of a spherical mirror is

30 cm. What is its focal length?
(a) 10cm (b) 15cm
(c) 20 cm (d) 25 cm

5. A ray of light travels from air to glass as shown Given that the refractive index of air is 1.0, what
below. is the refractive index of glass?
(a) 1.2 (b) 1.3
(c) 1.4 (d) 1.5
8. A light ray travels through three media as shown (iii) The principal focus of a lens always lies on
below. the principal axis.

(a) Only (i) and (ii) (b) Only (ii) and (iii)
(c) Only (i) and (iii) (d) (i), (ii) and (iii)
13. Which of the following statements are correct?
(a) The image distance obtained from a far away
object is the focal length of the convex lens.
(b) The images obtained from a convex lens
always lie on the focal point.
(c) The images obtained by a convex lens are
Which of the following shows the ascending always real.
order of their refractive indices? (d) The images obtained by a convex lens are
(a) Medium 1, medium 2, medium 3 always inverted.
(b) Medium 2, medium 3, medium 1 14. An object O is placed at the position shown in
(c) Medium 3, medium 1, medium 2 the given figure.
(d) Medium 1, medium 3, medium 2

9. Which of the following correctly shows how a

light ray travels through a thick converging lens?

(a) P (b) S What are the characteristics of the image

(c) Q (d) R formed?
(a) Real, inverted and diminished
10. Which of the emergent rays shown in the figure (b) Real, inverted and enlarged
is the correct-one, when an incident ray strikes a (c) Virtual, inverted and diminished
diverging lens? (d) Virtual, upright and enlarged
15. An object O is placed at the position shown in
the given figure.

(a) P (b) S
(c) R (d) Q

11. What is focal length?

(a) The distance from the light source to the
image What are the characteristics of the image
(b) The distance from the object to the centre of formed?
the lens (a) Real, inverted and diminished
(c) The distance from the image to the centre of (b) Real, inverted and enlarged
the lens (c) Virtual, upright and enlarged
(d) The distance from the focal point to the (d) No image is formed
centre of the lens 16. A converging lens has a focal length of 15 cm.
Given that an object is placed 10 cm from the
12. Which of the following statements are optical centre of the lens, what are the
characteristics of the image formed?
(i) The principal focus of a converging lens is (a) Real, inverted and diminished
real. (b) Real, inverted and of the same size as the
(ii) The principal focus of a diverging lens is object
virtual. (c) Real, inverted and enlarged
(d) Virtual, upright and enlarged

2
17. An object 0 and its image I drawn to scale are 21. A camera uses a converging lens to produce an
shown below. image on the film. If the focal length of the lens
is 10 cm, where can an object be placed from
the camera for taking a photograph?
(a) 10cm (b) 15cm
(c) 25cm (d) None of the above

22. When is refraction of light NOT possible?

(i) The angle of incidence is 0 .

Identify the correct position of the converging
(ii) The two media have the same refractive
lens.
index.
(a) P (b) Q
(iii) The refractive index is higher than 3.0.
(c) R (d) S

18. A light ray is parallel to the principal axis of a (a) Only (i) and (ii) (b) Only (ii) and (iii)
converging lens as shown below. (b) Only (i) and (iii) (d) (i), (ii) and (iii)

23. Which of the following does NOT affect the focal

length of a convex lens?
(a) Refractive index of the material for making
the lens
(b) Material of the lens
(c) Object distance
(d) Thickness of the lens
Identify the correct position of the emergent ray.
24. In an experiment to determine the focal length of
(a) Q (b) R
a converging lens, the object distance and the
(c) P (d) S
image distance recorded were 20 cm and 30 cm
respectively. What is the focal length of the
19. An object 0 is placed at the position shown in
converging lens?
the given figure.
(a) 10 cm (b) 12 cm
(c) 15 cm (d) 18cm

25. During the refraction of light, which of the

following quantities remains constant?
(a) Wavelength (b) Speed
(c) Frequency (d) Both (a) and (b)

26. A converging lens magnifies a real image to four

What are the characteristics of the image times its original size. Given that the focal length
formed? of the converging lens is 20 cm. what is the
(a) Real, inverted and diminished object distance?
(b) Real, inverted and of the same size as the (a) 5 cm (b) 25 cm
object (c) 40cm (d) 100cm
(c) Real, inverted and enlarged
(d) Virtual, upright and enlarged 27. A converging lens magnifies a virtual image to
four times its original size. Given that the focal
20. Find the position, nature and size of the image length of the converging lens is 20 cm, what is
formed when an object of size 1 cm is placed at the object distance?
a distance of 15 cm from a concave mirror of (a) 5cm (b) 10cm
focal length 10 cm. (c) 15cm (d) 25cm
(a) On the left side, 30 cm, real, inverted and
magnified 28. A concave mirror is made by cutting a portion of
(b) On the left side, 20 cm, virtual, upright and a hollow glass sphere of radius 24 cm. Find the
diminished focal length of the mirror.
(c) On the right side, 30 cm, real, inverted and (a) 24cm (b) 12cm
magnified (c) 6cm (d) 18cm
(d) On the right side, 20 cm, virtual, up- right
and diminished

3
29. At which of the following positions do the given 35. Identify a mirror which neither converges or
mirrors form a virtual image? diverges a parallel beam of light rays falling on it.
(a) In convex mirror at infinity (a) Plane mirror
(b) In concave mirror between F and P (b) Convex mirror
(c) In plane mirror at all positions (c) Concave mirror
(d) All the above (d) Convexo-Concave mirror

30. An object is placed at the centre of the curvature 36. Where should an object be placed so that a real
of a concave mirror. What is the distance and inverted image of the same size is formed by
between its image and the pole? a convex lens?
(a) Equal to f (b) Between f and 2 f (a) At infinity
(c) Equal to 2 f (d) Greater than 2 f (b) At the focus of the lens
(c) At twice its focal length
31. A ray of light is incident on a concave mirror. If it (d) Between f and the lens
is parallel to the principal axis, what happens to
the reflected ray? 37. If a real object is placed in front of a convex lens
(a) t will pass through the pole. of focal length 'f at its principal focus, where is
(b) It will pass through the centre of curvature. the image formed?
(c) It will pass through the focus. (a) At zero (b) At infinity
(d) It will retrace its path. (c) At a distance of 2f (d) At a distance f/2

32. What is the distance between a real object and 38. Which of the following always produces a
its real image in the case of a concave mirror, diminished image of an object?
when the object is placed at the centre of (a) A convex mirror (b) A concave mirror
curvature? (c) A convex lens (d) Bi-convex lens
(a) f (b) 2f
(c) 4f (d) Zero 39. A monochromatic beam of light passes from a
denser medium into a rarer medium. What is the
33. Which of the given mirrors can be used to get an result?
image larger than the object? (a) Its velocity increases.
(a) A convex mirror (b) Its velocity decreases.
(b) A concave mirror (c) Its frequency decreases.
(c) Either a convex or a concave mirror (d) Its wavelength increases.
(d) A plane mirror
40. In which mirror does one find the image long
34. If an incident ray passes through the centre of and thin?
curvature of a concave mirror, what happens to (a) Concave mirror (b) Convex mirror
the reflected ray? (c) Cylindrical mirror (d) Parabolic mirror
(a) It will pass through the pole of the mirror.
(b) It will pass through the focus of the mirror.
(c) It will retrace its path.
(d) It will be parallel to the principal axis.

4
 Previous contest Questions
1. By using which of the following mirrors can you (b) A concave lens of focal length 50 cm.
burn a piece of paper using the reflected rays of (c) A convex lens of focal length 5 cm.
the sun? (d) A concave lens of focal length 5 cm.
(a) A plane mirror (b) A concave mirror
(c) A convex mirror (d) All of the above 8. A ray of light travels from water to glass as
shown below. The refractive index of water is
2. When sun rays are focussed with a convex lens, 1.3 and the refractive index of glass is 1.5.
a sharp, bright spot is observed at its focus. What
does this spot indicate?
(a) The real image of the sun
(b) The virtual image of the sun
(c) An optical illusion produced by the convex
lens
(d) The magnified image of the sun

3. Which of the following statements is NOT

correct? What is the angle of refraction?
(a) A medium with larger refractive index is (a) 30.7 (b) 35.3
optically denser than a medium with smaller (c) 41.7 (d) 48.6
refractive index.
(b) The speed of light is less in a rarer medium 9. Two light rays travelling parallel to the principal
than a denser medium. axis strike a converging lens and meet at a point
(c) Refraction is due to the change in speed of as shown.
light as it enters from one medium to another.
(d) The absolute refractive index of a medium is
simply called its refractive index.

4. A ray of light is incident on a plane mirror at an

angle of incidence 30° to the normal. With what
angle is the ray deviated, after reflection?
(a) 30 (b) 60 Which point is called the focal point?
(c) 90 (d) 120 (a) R (b) P
(c) Q (d) S
5. Only one of the following applies to a concave
lens. Identify it. 10. An incident ray strikes a rectangular glass block
(a) The focal length is positive. as shown below.
(b) The object distance can be positive or
negative.
(c) The height of the image can be positive or
negative.
(d) Image distance is always negative.

6. In which of the following is the focal length

always positive?
(a) Plane mirror (b) Concave lens Which of the given emergent rays is the correct
(c) Convex lens (d) All of the above one?
(a) E1 (b) E2
7. Which of the following lens would you prefer to (c) E3 (d) E4
use while reading small letters found in a
dictionary?
(a) A convex lens of focal length 50 cm.

5
 Answers with Solutions
Multiple Choice Questions

1. (a) The angle of reflection is the angle between 11. (d) Focal length is the distance from the focal
the normal and the reflected ray. point to the centre of the lens.
90  70  20.
12. (d) All the three statements are true.
2. (c) At point R, the image of object 'O' is formed.
13. (a) Statement (a) is correct.

14. (d) When u < f, the image formed is always

virtual, upright and enlarged (magnified) as per
the given figure on pg. 13.

15. (d) When u = f, there is no image formed as the

light rays do not get converged or diverged as
per the given figure on pg. 13.
3. (a) As per the given figure on page 11,
ni sin i  nr (1.3)sin(i)  (1)sin30o 16. (d) Focal length f is 15 cm. As u < f, the image
formed will be virtual, upright and magnified.
13 1
sin i   0.3846, i  22.6o
10 2 17. (b) Q is the correct position of the lens as per the
given figure on pg. 13.
R 30
4. (b) f    15 cm 18. (d)As per the given figure on pg. 14, the correct
2 2
position of the emergent rays is S.
5. (c) As per the given figure on page 11,
19. (b) When u = 2f, the image formed is always
ni sin i  nr sin r,(1)sin(i)  60o  (1.5)sin(r ) real, inverted and of the same size as the object
3 as per the given figure on pg. 13
 1  1.5  sin(r ),
2
sin r  0.577, r  35.3 20. (a)
1 1 1 1
  , we get: 
1

1
v u f v 15 10
6. (a) Option (a) correctly represents the respective 1 2  3 1 1
rays in the given glass slab.  , 
v 30 v 30
So, image distance, v = -30 cm on the left side
7. (d) As per the given figure on page 12,
of the mirror. It is real, inverted and magnified.
n1 sin i  nr sin r ,(ni )sin 40o  (1)sin 74.6o
sin 74.6o 0.9617 21. (c) The image obtained from a camera is real,
n1   n1  1.5 inverted and diminished. To get such an image,
sin 40o 0.6727'
it must be a case of u > 2f.This implies that u >
8. (c) When a light ray travels from one medium to 20 cm. The object can placed at 25 cm from the
another medium, the more the light ray is camera for taking a photograph.
refracted away from the normal, the lesser is the
refractive index of that medium. 22. (a) The refractive index in higher than 3.0 is
incorrect. As long as the i is not 0 and there is
9. (a) As per the given figure on page 12, a difference between the refractive indices of the
Converging lens P correctly shows the incident two media involved, refraction will take place.
ray refracting towards the normal when it travels
from air to glass. It also refracts away from the 23. (c) The object distance does not affect the focal
normal when it travels from glass to air. length which is a property of the lens.

10. (a) As per the given figure on page 12, Emergent 24. (b) By using the lens equation,
1 1 1
 
ray P is the correct one when an incident ray u v f
strikes a diverging lens.

6
 1 1 1 1 1 1
     32. (d) When the object is placed at C of a concave
20 30 f f 20 30
mirror, the distance between a real object and its
1 3 2 5 real image is zero.
    f  12 cm
f 60 60
33. (b) To get an image larger than the object i.e., a
25. (c) During the refraction of light the quantities magnified image, one can use a concave mirror
wavelength and speed change. Frequency is because it forms a magnified, real and inverted
always a constant quantity in the case of light. image when the object is placed at F of the
mirror.
1 1 1
26. (b) By using the lens equation,   34. (c) The reflected ray retraces its path in the same
u v f
direction because it strikes the mirror at right
1 1

1 5 1
 ,  , u  25 cm angles (90) to its surface due to which the angle
u 4u 20 4u 20 of incidence and reflection are 0 .

1 1 1 35. (a) When a parallel beam of light rays fall on a

27. (c) By using the lens equation,  
u v f plane mirror, it neither converges or diverges as
its focal length is said to be infinite or at infinity.
1 1 1 3 1
    , u  15 cm It means that it is limitless.
u 4u 20 4u 20
Take note that a negative sign must be added to 36. (c) To obtain a real, inverted image of the same
the image distance if the image is a virtual size, the object must be placed at 2for twice the
image. focal length of the convex lens.

Radius of curvature 24 37. (b) When a real object is placed infront of a

28. (b) f    12 cm
2 2 convex lens of focal length 'f at its principal
focus, then the image is formed at infinity.
29. (d) All the given mirrors form a virtual image of a 1 1 1 1
   ,  0 (or) v  
real object according to the giver positions. f v f v

38. (a) A convex mirror always produces only virtual

30. (c) An object is placed at C,  u  C  2 f and diminished images of objects.
1 1 1
Mirror formula,   39. (a) When a monochromatic beam of light passes
f u v
from a denser medium to a rarer medium, its
For concave mirror, f = negative
velocity increases and wavelength decreases, but
1 1 1 1 1 1 frequency remains constant.
   ,  
f 2f v v f 2f
1 1 40. (c) In a cylindrical mirror, one finds his image
  v  2 f long and thin.
v 2f

31. (c) When a ray of light is incident and parallel to

the principal axis, after reflection it will pass
through the focus of the mirror.

7
 Previous Contest Questions
1. (b) A concave mirror can be used to burn a
piece of a paper by focusing reflected rays of the
sun.

2. (a) A parallel beam of sun rays get converged by

a convex lens as a sharp, bright spot. This is the
real image of the sun.

3. (b) The speed of light is higher in a rarer

medium than in a denser medium.

4. (a) Given i  30o , As i  r , r  30o

5. (d) For a concave lens, the image distance is

always negative.

6. (c) Focal length is always positive for a convex

lens.

7. (c) A convex lens of focal length 5 cm.

8. (d) As per the given figure on pg. 16,

ni sin i  nr sin r ,(1.3)sin 60o  (1.5)sin(r )

13 3 3
   sin r ,sin r  0.577, r  48.6o
10 2 2

9. (d) As per the given figure on pg. 16, Point S is

called the focal point on the principal axis where
the light rays converge.

10. (b) The correct emergent ray is E2