SMTP Sec 3
Term 1 Test
Physics Revision Questions
Refraction & Total Internal Reflection
6.
The set-up shown below is used to determine the refractive index and critical angle of glass.
O is the centre of the circular plate graduated in degree and is also the centre of the semi-circular
glass block. R is a ray box which is always directed towards O. The values of angle x and y are
recorded in the following table.
x/o
10
20
30
40
50
60
70
80
y/o
16
30
53
140
130
120
110
100
(a)
Does the light ray bend at the circular face? Explain briefly.
[2]
No, the light ray does not bend/ remains undeviated.
[1]
This is because the angle of incidence is 0o, hence the light ray enters
the glass undeviated. (angle of refraction is 0o)
[1]
Created by Ms Adeline Tan
(b)
Use the first pair of data (x and y) to calculate the refractive index of glass.
[2]
Refraction index of glass
(c)
= sin 16o / sin 10o
= 1.6
[1]
[1]
Explain briefly the strange behaviour when x increases from 30o to 40o.
[2]
When x = 40o, angle of incidence is greater than the critical angle
(c = 39o).
[1]
Hence, total internal reflection occurs.
(d)
[1]
What is the value of y when x = 45o
y = 180o- 45o
=135o
[2]
[1]
[1]
(e)
One of the values of y is recorded wrongly. Calculate the correct value.
[2]
1.59 = sin y / sin 20o [1]
sin y = 0.5438
y = 33o
[1]
(f)
If R is moved between D and A, how would the refracted ray OP move?
[2]
OP will be refracted towards the normal in glass
but leaves the glass boundary undeviated into air.
[1]
[1]
7. The figure below, not drawn to scale, shows the behaviour of a ray of light passing in different
media as it passes from 1 medium to another.
Created by Ms Adeline Tan
medium 1, 1  1.30
medium 2
medium 3
medium 4, 4  1.0
(a) If you were to place yourself in medium 4, would you be able to see this ray of light which
originates from medium 1 as shown? Why?
[3]
No [1]
Since the ray does not reach medium 4 [1] because at the boundary the angle that it makes
with the normal is equal to the critical angle [1]
(b) If the ray of light is replaced by an extended illuminated object. Now, would you be able to
see it in medium 4? [An extended illuminated object will emits many rays of light in all
directions]
[1]
Yes [1].
(c) Given that the ray of light in medium 1 and 3 are parallel, determine refractive index of
medium 3.
[1]
1.30 [1]
(d) Calculate the critical angle, c, between medium 3 and 4
[2]
Using Snell's Law,
i sin i = r sin r
(1.30)sin c= (1.0)sin 900
[1]
 c =50 (2 sf)
[1]
(e) If there is a requirement to make sure the light ray will pass through from 1 medium to
another without refraction, suggest a method to achieve this requirement. Explain your
answer.
[2]
Ensure the light ray hits the surface along the normal OR angle of incidence equal to zero.
[1]
Created by Ms Adeline Tan
Since the angle of incidence is zero, the angle of refraction will be zero [1] as well, the light
ray will pass through undeviated.
8. A boy dived into a swimming pool. While he was still in water, at position E, he noticed a bird
flying across. The apparent height where the bird is observed is
happarent = 18.0 m. Given that air  1.00 and the bird is observed at hreal=11.0 m above the water.
happarent
Bird
hreal
air  1.00
 water
E
(a) Which medium has a greater refractive index?
Water [1]
[1]
(b) Calculate the refractive index of water relative to that of air
[2]
 water 
apparent depth
actual depth
18.0

[1]
11.0
 1.636363
= 1.64 (3 sf)
[1]
(c) Determine the speed of light in water.
Take speed of light in air to be 3.0 x 108 m/s
medium1 
[2]
speed of light in air
speed of light in water
1.636363 
3.0 108
speed of light in water
speed of light in water  1.8 108 m/s (2 sf)
Created by Ms Adeline Tan
[1]
[1]
Measurements & Units
9. Read the following technical specifications and answer the following questions.
Source: http://www.appletidbits.com/ipoddbspec.php?display=72
Some points to take note of:




bit is usually written in b
Byte is usually wriiten in B
8 bit = 1 Byte
1kiloByte = 1000 Byte
(a) Which instrument could have been used to measure the thickness of 1.05cm?
Vernier Calipers
[1]
Micrometer Screwgauge
(b) Convert 10.3cm to nm
10.3 cm = 1.03 x 108 nm
[1]
OR
= 10.3 x 107 nm
(c) Calculate the density of this player, express your answer in kg/m3.
[2]
9
1 m =10 nm
1 m3  1027 nm3
1027 m3  1 nm3
Therefore 6.7053 1022 nm3  6.7053 1022 10 27 m3  6.7053  105 m3
mass
Density =
volume
0.14 kg
=
[1]
6.7503 10-5 m3
=2.1 103 kg/m3 (2 sf)
[1]
Created by Ms Adeline Tan
(d) Based on the capacity of this player, what is the average file size of a song, in terms of MB?
[1]
Total file size
Size of each file/ song =
No. of song
120 109 B
30000
= 4 MB
=
[1]
(e) Assuming a movie takes up 700 megabyte (MB) of disk space. How many full length movies can
this player hold?
[1]
9
120 10
No. of full movies =
 171.4  171
700 106
(f) Given that each movie (700MB) takes 2 hours to be downloaded. On the average, how much is
the rate of transfer of data in terms of kbps (kilobit per second) from the source to the player?
[2]
700 MB
700  106 B
=
2 hr
2  60  60s
700  106  8b
=
2  60  60s
700  103  8kb
=
2  60  60s
= 777.778 kbps
= 800 kbps (1sf)
Created by Ms Adeline Tan
[1m for correct coversion of unit]
[1]
Lens
10. The figure shows two rays diverging after passing through a converging lens.
[1 m each, for both the apparent ray]
F, principal focus
[1]
[1]
*[-1 overall if arrows are not shown for the real rays]
*[award 0 if virtual rays are drawn using solid lines]
*[award 0 if real rays are drawn using dotted lines]
(a) Complete the diagram to show
(i) the point from which the rays have actually come from.
(ii) the point from which the rays appear to come from,
[4]
(b) Is the image virtual or real? Explain your answer.
[2]
Virtual [1].
Since the object distance, u, is less than f, the focal length
OR
[1]
The image is not formed on the screen
OR
No light meet at the image position
(c) If the lens is moved towards the object, state how the image would change
Image is nearer to lens than before
[1]
The new image appears smaller than the previous image [1]
Created by Ms Adeline Tan
[2]
11.
The figure below shows an object AB placed in front of a convex lens. P, Q, R are
rays incident on the lens.
(a)
Draw the three refracted rays on the given diagram and locate the image.
[3]
- Draw 3 rays [2m]
- Locate image [1m]
Note: did not use dotted lines
for rays and image [deduct 1m]
(b)
State the nature of the image.
[1]
The image is virtual.
(c)
Draw a ray, in the diagram given, which goes from point B to the eye.
[1]
Created by Ms Adeline Tan
[Any one ray]
END
Created by Ms Adeline Tan