F3 I.S.
Remedial programme
Problem set 03/10
Score:
/ 30
Unit 3 Light, colors and beyond
A
True or false questions (6 marks, 1 mark each)
Write ‘T’ for a true statement and ‘F’ for a false statement in the boxes provided.
1
When light travels from air to water, light ray bends away from the normal.
2
Light travels faster than sound in air.


3
The speed of light in water is faster than air.

4 When light travels from air to water, if the angle of incidence is 0°, the angle
of refraction will be also 0°.
5

Refraction only occur when light travel from air into water or glass.

6 According to laws of refraction, the angle of incidence is equal to the angle of

refraction.
B
Multiple-choice questions (6 marks, 2 marks each)
Choose the correct answer for each of the following questions.
1
Which of the following diagrams correctly show(s) the path of light ray passing
from air into water?
(I)
(II)
(III)
A.
B.
C.
D.
air
water
(I) only
(I) and (II) only
(II) and (III) only
(I), (II) and (III)
air
water
air
water
1

2
Which of the following phenomena are caused by refraction of light?
(I) A swimming pool appears shallower than it really is.
(II) A metre rule appears bent when dipped in water.
(III)A spectrum( different colour spread out) is formed when white light passes
through a prism.
A.
B.
C.
D.
(I) and (II) only
(I) and (III) only
(II) and (III) only
(I), (II) and (III)

3
A light ray strikes the straight edge of a semi-circular glass block as shown.
Which of the following diagrams is correct?
A.
B.
C.
D.

2
C Fill in the blanks (6 marks, 1 mark each)
Complete the following sentences.
1
When light travels from optical _________________________ (for example, glass)
to optical
_________________________ (for example, air), light ray bends away
from the normal.
2
The
_________________________ (n)
of a medium is given by speed of light in vacuum
divide by the speed of light in the medium.
3
The refraction of light is due to the difference in its ____________________ in
different media.
4
Due to refraction of light,
the apparent depth of a pool is ____________________ than the real depth of the
pool.
a chopstick in water appears to be ____________________.
D Questions (12 marks)
1
State the laws of refraction.
(4 marks)
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
3
2
In the figure below, the two rays represent the cone of rays coming from the
spotlight which is fixed at the bottom of the pool.
(a) Complete the paths of the two light rays in the air.
(2 marks)
(b) Use the answer in part (a) to explain why the pool appears to be shallower than it
actually is.
(2 marks)
4
3
A ray of red light and a ray of violet light travel from air to a glass block at the same
angle of incidence of 30° as shown. Suppose that the refractive indices of the glass
are 1.610 and 1.615 for red light and violet light respectively.
(a) Find the angles of refraction of
(i) red light; and
(ii) violet light in the glass.
(3 marks)
(b) Calculate the angle θ.
(1 mark)
- End –
5
Answers
Unit 3 Light, colors and beyond
F3 I.S.
Remedial programme
Problem set 03/10
A True or false questions (6 marks, 1 mark each)
1 F
2 T
3 F
4 T
5 F
6 F
B Multiple-choice questions (6 marks, 2 marks each)
1 B
2 D
3 B
C Fill in the blanks (6 marks, 1 mark each)
Denser, less dense
Refractive index
Speed
Shallower, bent
D Questions (12 marks)
Answer:
1 The incident ray, refraccted ray and the normal all lie in the same plane.
The ratio of sin i to sin r is a constant. Mathematically,
sin i
 constant
sin r
2
(a)
(2A)
6
(b) As observed from the answer in part (a), the light from the bottom of the pool is
bent (1A) when it comes across the water-air boundary. When we trace back the path
of the light rays above the water, we find that the light rays come from a position
higher than the bottom of the pool (1A). This explains why the pool appears to be
shallower than it actually is.
3
(a) The angle of refraction for red light is
sin i
sin r
sin 30
1.610 
sin r
r  18.0929
 18.1
n
(1M+1A)
The angle of refraction for violet light is
sin i
sin r
sin 30
1.615 
sin r
r  18.0350
 18.0
n
(b)  = 18.0929 − 18.0350 = 0.0579°
(1A)
(1A)
7