YUHUA SEM 3_STPM 2021

Form : 6AS1 SMJK Yu Hua, Kajang, Selangor
Date :21st April 2022 (Thursday) STPM Trial Examination
Time :11:25 am – 12:55 am Physics Paper 3
April 2022
Number of printed pages :
Prepared by : Pn Rosmaya binti Mokhtar

Verified by : Pn. Fazida binti Saipan @ Saipol

Section A. (15 marks)
Answer all questions.

1. An object of mass m undergoes a simple harmonic motion with frequency f and amplitude A. The maximum

restoring force is

A. fmA B. f2mA C. 22f2mA D. 42f2mA

2. The figure below shows two simple pendulums J and K having the same lengths and same sizes and a
simple pendulum L whose length can be varied.

The pendulum J and K will oscillate after the pendulum L is set into oscillations in a plane parallel to the
wall. Which of the following graphs below shows the variation of the amplitude A for the pendulum J and
the pendulum K with frequency f of the pendulum L when the length of the pendulum L is varied?

3. The transverse wave in a string is represented by the equation

y = 10 sin [(x – 0.2t)]

where x and y are measured in centimeters and t in seconds. The phase difference between two points 0.20

cm apart on the wave is

A. 0.11 rad B. 0.13 rad C. 0.20 rad D. 0.63 rad

4. The figure below shows the vibrations for the fundamental frequency, frequency of the first overtone and
frequency of the second overtone for a sound instrument.

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These vibrations can also be produced by
A. Striking a tuning fork
B. Blowing across the open end of a pen cover
C. Connecting a low alternating voltage to a loudspeaker
D. Plucking a stretched string

5. Three successive overtones emitted by a pipe are at frequencies 210 Hz, 350 Hz and 490 Hz. What is the

fundamental frequency?

A. 35 Hz B. 70 Hz C. 140 Hz D. 400 Hz

6. An audio source emitting sound at a frequency of 500 Hz is attached to the end of a rod of length

0.5 m. The rod is rotated in a horizontal circle with an angular of 50 rad s-1. What is the maximum

frequency of the sound received by a stationary observer. [speed of sound in air = 340 ms-1]

A. 500 Hz B. 537 Hz C. 540 Hz D. 579 Hz

7. A ray of light in a medium is incident towards the boundary of the first and second medium. Total internal

reflection occurs when the angle of incidence exceeds a certain value. Which of the following statements is
true concerning the incident ray?

A. The light is monochromatic
B. The light must be of sufficient intensity

C. The velocity of light in the first medium is less than the velocity of light in the second medium
D. The light’s frequency in the first medium is higher than the light’s frequency in the second medium

8. A concave lens of focal length 10 cm is placed next to another concave lens of focal length 20 cm. If a point
object is placed at the primary focus of the first lens, where would be the emerging ray emerge from if the
distance between the two lenses is 25 cm?
A. 5 cm from the first lens
B. 5 cm from the second lens
C. 10 cm from the first lens
D. 10 cm from the second lens

9. The figure shows a ray incident on a glass surface coated with a film.

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If the wavelength of light in the film is , and the refractive indices of the film and glass are n1 and n2
respectively, which of the following is the condition for destructive interference between the reflected rays
X and Y?
A. t =  where n1 > n2

4n
B. t =  where n1 >n2

2n
C. t =  where n1 < n2

2n
D. t =  where n1 < n2

n

10. The lens of a sunglasses is made up of lamination of two polaroid sheets with its axis of polarization making

an angle of 30o. Neglecting effect due to tint in the polaroids, what is the percentage of the intensity of

normal light can transmit through this lens?

A. 37 % B. 43% C. 75 % D. 87 %

11. The speed of light along the core of an optical fibre is 1.57x108 ms-1 and along the cladding is
1.67x108 ms-1.

What is the minimum angle of incidence of light in the core for it to be totally internal reflected?

A. 20o B. 32o C. 34o D. 70o

12. The variation of photoelectric current I with potential difference V across a photocell is shown in the graph
below.

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What is the maximum speed of the photoelectrons emitted?

A. 5.9x105 ms-1 B. 8.4x105 ms-1 C. 1.2x106 ms-1 D. 1.7x106 ms-1

13. The intensity and frequency of the incident light is increased by two times. Then which of the following is
true?
A. Photoelectric current will be increased by two times
B. Photoelectric current will be decreased by four times
C. Photoelectric current remains the same
D. Photoelectric current increases and then decreases

14. On increasing the number of electrons striking the anode of an X-ray tube, which one of the following

parameters of the resulting X-rays would increase

A. Penetration power B. Frequency C. Intensity D. Wavelength

15. An X-ray of wavelength 88 pm experiences maximum reflection of second order when it is

incident at an angle of 30o with the surface of a crystal . What is the separation between atomic

planes of the crystal ?

A. 44 pm B. 176 pm C. 88 pm D. 352 pm

Section B. (15 marks)
Answer all questions.

16. A transverse wave is given by

where x and y are in centimetres and t in seconds.
(a) Determine the speed of the wave. [3 marks]

(b) Determine the maximum transverse speed of a particle of the wave. [3 marks]

(c) Sketch the shape of the wave when t, is 0.125 s. [2 marks]

17. The “blooming” of a camera lens, involves coating its front surface with a thin layer of magnesium fluoride
of refractive index 1.38, increases the amount of light transmitted into the camera. The refractive index of
the camera lens is 1.61 and the wavelength of the light in air is taken as 550 nm.

(a) What is the wavelength of the light in magnesium fluoride? [2 marks]

(b) What is the minimum thickness of the magnesium fluoride coating for this purpose? [4 marks]

(c) How the coating helps to increase the amount of light transmitted? [1 mark]

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Section C.
Answer two questions in this section. [30 marks]
18. (a) (i) State two conditions for a simple pendulum to perform simple harmonic motion.

[2 marks]
(ii) Figure below shows the oscillation of a simple pendulum of length, L. Derive the period
of oscillations for simple pendulum system. [5 marks]

(b) The length of a simple pendulum is 1.0 m and it is released at an angle 8o to the vertical.
Calculate
(i) the frequency of the oscillation, and
(ii) the pendulum’s bob speed when it passes through the lowest point of the swing.

[5 marks]
(c) A tsunami warning siren on top of a tall pole radiates sound waves uniformly in all
directions. At a distance 20.0 m the intensity of the sound is 0.640 Wm-2. Determine the distance at which
the intensity is 0.040 Wm-2. [3 marks]
19. (a) (i) What is the characteristics of light which enables polarization to occur ? [1 mark]

(ii) A charged particle oscillating in the y –direction is shown in diagram below

If the electromagnetic wave propagates in the positive z –direction, state the direction of
the oscillation of the electric field E and magnetic field B components of the
electromagnetic wave produced. [2 marks]
(b) Unpolarised light with the electric component of amplitude E0 passing through two
polaroid in the diagram below.

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(i) What is meant by unpolarised light ? [2 marks]

(ii) Explain why, after the light passes through the first polaroid, the intensity of
the light is half of its original value even though the amplitude of the electric
component of light before and after passing through the first polaroid is the
same. [3 marks]

(iii) Calculate the angle, θ so that the original intensity of light can be reduced to
25% after passing through both polaroids. [5 marks]

(c) Light can be polarized by reflection. A light beam is directed to a glass surface with
a refractive index of 1.52. Calculate the incident angle so that the reflection of the light
beam is fully polarised. [2 marks]

20. (a) Explain the difference between quantum theory and wave theory for light. [2 marks]

(b) One of the observations in photoelectric effect experiment carried out by Millikan was the maximum
kinetic energy of the photoelectrons increases when light of higher frequency is irradiated on the photocell.
(i) With the aid of a labelled diagram for the experimental setup, explain how the maximum kinetic
energy of the photoelectrons can be determined. [4 marks]
(ii) Explain the observation above by using quantum theory. [3 marks]

(c) The graph below shows the variation of the maximum kinetic energy of the photoelectrons with the
frequency of the incident rays for different metals of photo cathode.

Based on the graph above,
(i) determine the value of Planck’s constant. [3 marks]

(ii) determine the work function for aluminium in Joule. [2 marks]

(iii) determine the threshold wavelength of Beryllium. [1 mark]

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Form : 6AS1 SMJK Yu Hua, Kajang, Selangor
Date :21st April 2022 (Thursday) STPM Trial Examination
Time :11:25 am – 12:55 am Physics Paper 3
April 2022
Number of printed pages :
Prepared by : Pn Rosmaya binti Mokhtar

Verified by : Pn. Fazida binti Saipan @ Saipol

Answer :
Section A.

1. D
2. A
3. D
4. D
5. B
6. C
7. C
8. A
9. B
10. A
11. D
12. B
13. A
14. C
15. B

Section B.

16. (a)

(b)

1

(c)

17. a)
b)
c) Less or no light is reflected ______________________1

Section C.
18. a) i)

2

ii)

c)

19. a) i) Light waves are transverse wave
ii) Direction of EM wave propagation is in the direction of the vector product,
E x B.
Direction of E-field +y direction, direction of B-field, -x direction or
Direction of E-field -y direction, direction of B-field, +x direction

3

b) i) Unpolarised light: Oscillations of the E-field (and B –Field) are in all possible
panes.
ii) Component of the electric field oscillations parallel to the polarization axis of
the polaroid are transmitted, but components perpendicular to the axis are
absorbed. / Therefore, only half of the energy is transmitted.
iii)

c)

20. a)

b) i)

b) ii)

4

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