2009 h2 physics - yjc.pdf

YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE

Candidate Name ………………………………….……… CTG ……………….…

YISHUN JUNIOR COLLEGE JC 2 Preliminary Examinations 2009

PHYSICS 9745/1 HIGHER 2

2 September 2009

Paper 1 Multiple Choice Wednesday 1 hour 15 minutes

Additional Materials: Optical Mark Sheet

INSTRUCTIONS TO CANDIDATES

Do not open this booklet until you are told to do so. Write your name and CTG on the Optical Mark Sheet in the spaces provided. Shade your CTG and OMR Register Number in the space provided. There are forty questions in this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Optical Mark Sheet. Read the instructions on the Optical Mark Sheet carefully. INFORMATION FOR CANDIDATES Each correct answer will score one mark. A mark will not be deducted for a wrong answer.

Any rough working should be done in this booklet.

This question paper consists of 22 printed pages.

9745/1/JC2Prelims/YJC2009

2

Data speed of light in free space, c = 3.00 108 m s–1

permeability of free space, o = 4 10–7 H m–1 permittivity of free space, o = 8.85 10–12 F m–1 (1/(36)) 10–9 F m–1

elementary charge, e = 1.60 10–19 C

the Planck constant, h = 6.63 10–34 J s unified atomic mass constant, u = 1.66 10–27 kg rest mass of electron, me = 9.11 10–31 kg

rest mass of proton, mp = 1.67 10–27 kg molar gas constant, R = 8.31 J K–1 mol–1

the Avogadro constant, NA = 6.02 1023 mol–1

the Boltzmann constant, k = 1.38 10–23 J K–1 gravitational constant, G = 6.67 10–11 N m2 kg–2 acceleration of free fall, g = 9.81 m s–2

Formulae

uniformly accelerated motion, s = ut + 2

1at2

v2 = u2 + 2as

work done on/by a gas, W = pV hydrostatic pressure, p = g h gravitational potential,

r

Gm

Displacement of particle in s.h.m. x = xo sin t velocity of particle in s.h.m., v = vo cos t =

)( 22 xxo

resistors in series, R = R1 + R2+……….

resistors in parallel,

R

1

........

11

21

RR

electric potential,

r

Q

o4

alternating current/voltage, x = xo sin t

transmission coefficient T = exp(2kd)

where k = 2

2 )(8

h

EUm

radioactive decay, x = xo exp(–t)

decay constant, =

2

1

6930

t

.

=

=

V =


3

1 A driver cell of voltage VD is used to determine the voltage VT of a test cell via a

potentiometer. The driver cell is labelled with a value (1.5 0.3) V. The resistance wire

has a length L of (0.980 0.001) m.

At balance condition, the balance length, d, is found to vary between 22.7 cm and 23.3

cm. Given that L

d

V

V

D

T , which is the correction expression for VT?

A (0.35 0.08) V

B (0.4 0.08) V

C (0.3 0.2) V

D (0.35 0.21) V

2 With reference to question 1, which of the following is the best way of reducing the

percentage uncertainty of d?

A Adding a resistor in parallel with driver cell.

B Adding a resistor in series with driver cell.

C Adding a resistor in parallel with test cell.

D Adding a resistor in series with test cell.

Driver Cell, VD

Resistance wire of length L

G

Test Cell, VT

Balance length, d


4

3 A multiple exposure photograph is taken for a sphere dropping vertically. The time

interval between each pair of successive exposures is always the same.

Taking downwards as positive, which graph best represents, the motion of the body over

this period?

A B

C D

acceleration

time

acceleration

time

velocity

time

time = 0 s

displacement

time


5

4 A skateboarder glides along a straight road and throws a balloon vertically upwards.

If effects of air resistance are significant, which diagram best represents the trajectory

of the ball seen by a stationary observer?

A B

C D


6

5 The specific heat capacity of a liquid, c, can be determined using electrical methods.

If the heat loss to the surroundings is significant but not accounted for during the

experiment, how would the experimental value of c be affected?

A It will be overestimated.

B It will be underestimated.

C It will vary randomly with time.

D It will not be affected.

6 An ideal gas of volume V at pressure p undergoes the cycle of changes shown in the

graph.

At which points are the gas coolest and hottest respectively?

coolest hottest

A X Y

B Y X

C Z X

D Z Y

p / 105 Pa

V / 10–3 m3

4

1

1 5

Y X

Z


7

7 Four different composite rods of uniform thickness are to be balanced horizontally on a

knife-edge. Each rod is made up of 50% material A and 50% material B, where B is

denser than A. Which scenario is unlikely to occur?

A B

C D

8 A horizontal plank of uniform density is supported by a metal cable as shown in the

diagram. The cable joins at Q, the midpoint of the plank, and R is the midpoint of

cable QS. What is the direction of the reaction force exerted by the hinge pin on the

plank?

A PQ B PR C RP D PS

P Q

R

S

hinge pin

plank

cable

Material A Material B

Legend:


8

9 In each of the four diagrams below, a force is applied horizontally on crate P so that

both crates P and Q accelerate along a frictionless surface. If m and a denote unit

mass and acceleration respectively, which scenario corresponds to the largest force

exerted by Q on P?

A B

C D

10 Which of the following scenarios involves an object (in bold) having the greatest

resistance to change in motion?

A Bringing a car to a stop from 20 m s1.

B Raising a 5.0 kg block through a vertical height of 1.0 m from the ground.

C Steering an aircraft into a runway at a constant speed.

D Stopping an alpha particle using a thick sheet of paper.

2m m

a

Q P

3m m

0.5a

Q P

m m

3a

Q P

2m m

2a

Q P P


9

11 A person pulls a loaded trolley such that both move at constant velocity.

Which of the following statements about work done is correct?

A Work done on the trolley by the cord is zero because the trolley is moving at

constant velocity.

B Work done on the person by the ground is positive.

C Work done on the person by the cord is positive.

D Work done on the trolley by the ground is positive.

12 A spring of spring constant k is compressed by a length x. When released, it projects a

smooth metal sphere of mass m up a 30 slope.

Determine the maximum height h which the ball rises.

A mg

kx

4 B

mg

kx

2 C

mg

kx

4

2

D mg

kx

2

2

h

30

cord trolley


10

13 A car is travelling at constant speed v on a road in a hilly region as shown. The tops

and bottoms of the hills have radii of curvature R. At which position is the driver most

likely to feel weightless?

A At the top of a hill when gRv

B At the top of a hill when gRv

C At the bottom of a hill when gRv

D At the bottom of a hill when gRv

14 A child whirls a ball at the end of a rope, in a uniform circular motion. Which of the

following statements is not true?

A The speed of the ball is constant.

B The resultant acceleration of the ball is constant.

C The momentum of the ball is tangential to the path of travel.

D The rate of change of momentum of the ball is perpendicular to the path of

travel.


11

15 A rocket blasts away from Earth. Which of the following graphs best represents the

gravitational force, g on the rocket with respect to the distance, r from the surface of

the Earth?

A B

C D

16 Which of the following explains why free hydrogen atoms are abundant in the Sun but

not on Earth?

A The mass of the Earth is lighter.

B The escape velocity of hydrogen atoms on Earth is higher.

C The internal energy of hydrogen atoms on Earth is lower.

D Most of the hydrogen atoms on Earth have undergone nuclear fusion.

g

r

g

r

g

r

g

r


12

17 The following diagram is used as a reference to Questions 17 and 18. It shows the

trace produced by a sound wave on a c.r.o. The time base is calibrated at 4.0 ms cm1.

The vertical sensitivity is set at 1.0 mV cm1.

What is the frequency of the sound wave?

A 0.063 Hz B 63 Hz C 89 Hz D 180 Hz

18 The vertical deflection of the waveform can be adjusted on the c.r.o. using a knob to

change the vertical sensitivity. The intensity of the original sound wave increases and

at the same time, the vertical sensitivity is adjusted to 2.0 mV cm-1, such that the same

waveform (in above diagram) is replicated on the c.r.o. screen. What is the new

intensity in terms of the original intensity Io?

A 0.25 Io B 2.0 Io C 2.8 Io D 4.0 Io

19 In a fairground shooting game, a player is firing at a moving target by using a gun that

fires by itself at random timings. The player has to point the gun in a fixed direction,

while the target moves from side to side in simple harmonic motion.

At which region should the player take a fixed aim to score the greatest number of hits

on the target?

A 3 B 1 or 5 C 2 or 4 D 1, 3 or 5

1 cm

1

target

2 3 4 5


13

f

amplitude

f

a

f

amplitude

fo f

amplitude

ao

fo

f

amplitude

fo f

amplitude

fo

20 A pendulum is constructed from a fixed length of light thread and a spherical,

polystyrene bob of low density. It is forced to oscillate in air at different frequencies f.

The following diagram shows how the amplitude of its oscillation varies with f.

The experiment is repeated in a partial vacuum. Which graph best represents the

variation with f of the amplitude?

A

B

C

D

21 Under which conditions will the bright fringes of a double-slit light interference pattern

be farthest apart?

distance between

slits distance from slits

to screen wavelength of

source

A small large short

B small large long

C large small short

D large small long

ao

ao ao


14

22 The diagram shows the formation of the first order spectrum when parallel rays of

monochromatic light fall perpendicularly on a sub-standard diffraction grating PQR. For part of the grating between P and Q, the angle of deviation is constant and the

diffracted rays emerge parallel. However, from Q to R, falls progressively as shown in the graph.

Which graph best shows how the grating interval d varies with x, the distance from

P?

A

d

P x

Q R 0

B

d

P x

Q R 0

C

d

P x

Q R 0

D

d

P x

Q R 0

P x

Q R

graph diagram

x

falling

parallel P

R

Q

0

mono-chromatic

light


15

23 An isolated point charge produces an electric field with magnitude E at a point 2.0 m

away from the charge. What is the distance from the charge when the field

magnitude is E/4?

A 0.50 m B 1.0 m C 4.0 m D 8.0 m

24 An electron is moved in a uniform electric field of strength E.

What is the work done against the electric force when the

electron moves a distance s along the path?

A + e E s cos 60

B + e E s sin 60

C e E s cos 60

D e E s sin 60

25 The diagram shows a rectangular block with dimensions t 2t 3t.

Electrical contact can be made to the block between opposite pairs of faces (for

example between the face labelled P and its opposite face).

Between which two faces would the maximum electrical resistance be obtained?

A The face labelled P and its opposite face.

B The face labelled Q and its opposite face.

C The face labelled R and its opposite face.

D The resistance is the same, whichever pair of faces is used.

E

60

s

t

2t

3t

P Q

R


16

26 Which of the following shows the I – V characteristics of a thermistor?

A B

C D

27 Visible light of various frequencies emitted from hydrogen gas is irradiated onto a

calcium plate in a photoelectric experiment to determine their corresponding stopping

potential VS. The graph shows two plots P1 and P2 corresponding to two longest

wavelengths of light.

Which point on the graph shows the possible result when the next lower wavelength is

used?

V

I

V

I

V

I

V

I

VS / V

P1

f / Hz

P2

A

B C

D


17

28 A power supply is connected to a set of four identical resistors. Which of the following

arrangements corresponds to the maximum power delivered across PQ?

A B

C D

29 Which unit is equivalent to weber?

A volt second –1

B tesla metre –2

C kilogram metre 2 ampere

D joule ampere –1

P Q P Q

P Q P Q


18

30 Two long, parallel wires X and Y carry currents of I and 2I respectively.

The wire experiences

A attractive forces of same magnitude.

B attractive forces, but force on Y is greater than force on X.

C repulsive forces, but force on Y is greater than force on X.

D repulsive forces, but force on X is greater than force on Y.

31 A uniform magnetic flux of flux density 0.52 T passes at an angle of 60 to a horizontal

thin rod as shown.

When the metre-long rod is moved vertically upwards at a speed of 0.75 m s –1, what is

the magnitude of e.m.f. induced in the rod?

A 0 V

B 0.20 V

C 0.34 V

D 0.39 V

B = 0.52 T

60

2 I

I X

Y

0.75 m s –1


19

32 The magnetic flux linkage through a coil varies with time as shown.

Which graph shows the variation with time of the e.m.f. generated by the coil?

A B

C D

e.m.f.

time

e.m.f.

time

e.m.f.

time

e.m.f.

time

flux linkage

time


20

33 A rectifier is connected in series with load P and an alternating voltage supply as shown in

the figure below.

What is the value of the r.m.s. voltage across load P?

A 0.18 Vo B 0.35 Vo C 0.50 Vo D 0.71 Vo

34 In the diagram shown, the average power dissipated across a 2.0 resistor is 50 W.

What is the r.m.s. potential difference across the primary coil of the ideal transformer?

A 20 V B 40 V C 200 V D 400 V

P

Vin Vin / V

t / s Vo

240

2000 turns

50 turns

2.0

t 2t 3t 4t


21

35 A photon of energy 3.5 10–19 J falls on the cathode of a photocell. The work function

energy of the cathode is 3.1 10–19 J.

What is the stopping potential?

A 0.24 V

B 0.25 V

C 0.40 V

D 0.46 V

36 The diagram shows the electron energy levels for four different isolated atoms A, B, C

and D.

Which atom can produce radiation of the shortest wavelength when atoms in the ground

state are bombarded with electrons of energy W?

37 Which of the following statements about the energy gap of an intrinsic semiconductor is

incorrect?

A The energy gap is the energy separation between the bottom of the conduction

band and the top of the valence band.

B The energy gap usually carries a magnitude in electron volts.

C The energy gap can vary between different elements under Group IV of the

periodic table.

D The energy gap can be reduced by introducing dopant atoms.

A

W

B C D

Ground state


22

38 Which of the following is not a necessary condition for lasing action?

A Population inversion occurs between a metastable state and a lower lasing

state.

B Photons that trigger stimulated emission must carry the same energy as the

difference between a metastable state and a lower lasing state.

C The atoms of the lasing medium must stay at the ground state long enough for

external energy source to cause excitation.

D Emitted photons are confined long enough between two reflecting surfaces to

allow them to stimulate further emission for other excited atoms.

39 Which of the following best associates with decay constant of a radioactive source?

A It increases with number of radioactive nuclei.

B It increases with temperature.

C It is independent of time elapsed.

D It is independent of the element.

40 The count rate observed from a radioactive source at three different timings are as

follows:

t / s count rate / s –1

0 1600

6.0 X

8.0 100

What is the value of X?

A 150 B 200 C 300 D 400

~ END OF PAPER 1 ~

9745/2/JC2 Prelims/YJC2009

YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE YISHUN JUNIOR COLLEGE

Candidate Name ………………………………. CTG ……….…



20 August 2009 Paper 2 Thursday

1 hour 15 minutes

INSTRUCTIONS TO CANDIDATES Write your name and CTG in the spaces at the top of this page. Answer all questions. Write your answers in the spaces provided on the question paper. For numerical answers, all working should be shown clearly. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question.


For Examiner’s Use

1 /9

2 /9

3 /9

4 /9

5 /9

6 /15

Penalty

Total /60

Candidates answer on the Question Paper. No Additional Materials are required.

2



permeability of free space, o = 4 10–7 H m–1

permittivity of free space, o = 8.85 10–12 F m–1

(1/(36)) 10–9 F m–1


the Planck constant, h = 6.63 10–34 J s

unified atomic mass constant, u = 1.66 10–27 kg

rest mass of electron, me = 9.11 10–31 kg

rest mass of proton, mp = 1.67 10–27 kg

molar gas constant, R = 8.31 J K–1 mol–1


the Boltzmann constant, k = 1.38 10–23 J K–1

gravitational constant, G = 6.67 10–11 N m2 kg–2

acceleration of free fall, g = 9.81 m s–2

Formulae


1at2

v2 = u2 + 2as

work done on/by a gas, W = pV

hydrostatic pressure, p = g h

gravitational potential,

r

Gm

Displacement of particle in s.h.m. x = xo sin t

velocity of particle in s.h.m., v = vo cos t

= )( 22 xxo



R

1

........

11

21

RR

electric potential,

r

Q

o4



where k = 2

2 )(8

h

EUm


decay constant, = 2

1

6930

t

.

=

=

V =

3


For Examiner’s

Use

1 (a) Define work done on a body.

……………………………………………………………………………………….................

……………………………………………………………………………............................... [2]

(b) A skier starts from rest at A, and glides down a smooth slope. The dimensions of the

slope and the skier’s motion are illustrated in Fig.1.1. The skier passes through B, C, D,

E and reaches point F, R metres away from the cliff.

The effect of air resistance can be ignored in this scenario.

(i) Draw an arrow on Fig.1.1 to show the net force acting on the skier

1. at B (label as FB),

2. at E (label as FE). [2]

(ii) Show that the skier’s speed at C is 22 m s –1.

[2]

(iii) The skier leaves C at an angle of 35 above horizontal. Calculate R.

R = ………………… m [3]

B

A

C

D

E

F

R

30 m

5 m

10 m

skier

Fig. 1.1

4


For Examiner’s

Use

2 (a) (i) State the principle of conservation of momentum.

………………………………………………………………………………………..............

……………………………………………………………………………........................ [2]

(ii) In a science-fiction movie, a superhero in mid-air throws a heavy fridge towards a

villain on the ground. Using the answer in (a)(i), explain why the superhero cannot

remain stationary after the throw.

………………………………………………………………………………………..............

……………………………………………………………………………........................ [1]

(b) In a telematch, players need to catch as many eggs as possible, without breaking them,

using a big piece of towel. The egg is thrown towards the players one at a time.

(i) Discuss why a towel is suitable for performing the task described in (b).

………………………………………………………………………………………..............

…………………………………………………………………………….............................

……………………………………………………………………………........................ [2]

(ii) At a particular instant, an egg of mass 20 g reaches a piece of towel at a speed of

8.0 m s1.

1. Determine the impulse acting on the egg when it reaches the towel.

impulse = ……………………… N s [2]

2. Calculate the average force exerted by the towel in the attempt to bring the egg

safely to a stop in 1.5 s.

average force = ……………………… N [2]

5


For Examiner’s

Use

3 Hummingbirds (see Fig. 3.1) can hover around flowers by beating their wings at a frequency

between 20 to 80 times per second. It can be assumed that the air molecules around the birds

vibrate at the same frequency.

Fig. 3.1

(a) Deduce why a person who stands near a hovering hummingbird may hear a buzzing

sound.

………………………………………………………………………………………........................

………………………………………………………………………………………........................

………………………………………………………………………………………........................

……………………………………………………………………………............................... [2]

(b) A bird-watcher is initially 2.0 m from a hummingbird. To pick up a louder buzz, the bird-

watcher moves nearer to the bird by a distance x. Determine the value of x in metres for

an increased intensity of 60%.

x = ……………… m [3]

6


For Examiner’s

Use

(c) It is assumed that for a hummingbird which beats its wings at 75 times per second, the air

molecules around it can vibrate in simple harmonic motion at an amplitude of 5.0 10-9 m.

(i) Determine the maximum speed of vibration of the air molecules.

speed = …………………….. m s1 [2]

(ii) Calculate the distance covered by an air molecule over the duration in which the

hummingbird beats its wings for 1800 times.

distance = …………………….. m [2]

7


For Examiner’s

Use

4 (a) X-rays are emitted when a metal target placed in vacuum is bombarded with high energy

electrons. The variation with wavelength, , of the relative intensity of the X-rays is shown

in Fig. 4.1.

On the horizontal axis of Fig. 4.1, indicate the wavelength corresponding to the maximum

photon energy associated with the following processes:

1. Slowing down of the high energy electrons (label as A)

2. Electron transitions between the deep-lying energy levels of the atoms (label as B)

[2]

(b) Experimental results on alpha-decay indicate an inverse relationship between the kinetic

energy E of the alpha-particles and the half-life t½ of the radioactive source.

For observed E between 4 to 9 MeV, t½ varies between 1020 and 10–7 seconds.

(i) Show, with appropriate calculations, that E and t½ cannot be related in the form of

E =

21t

k , where k is a constant. [1]

relative intensity

wavelength,

Fig. 4.1

8


For Examiner’s

Use

(ii) The concept of quantum tunnelling is used to account for this inverse relationship.

An illustration used in conjunction with this concept is shown in Fig. 4.2. The

wavefunction of a 10-MeV alpha-particle is shown and the shaded region

represents the potential barrier encountered by the alpha-particle.

Fig. 4.2

1. Explain what is meant by quantum tunnelling.

………………………………………………………………………………………..........

……………………………………………………………………………........................

……………………………………………………………………………........................[2]

2. Deduce from Fig. 4.2, why the alpha-particle has a non-zero probability of

tunnelling through the potential barrier.

……………………………………………………………………………........................

……………………………………………………………………………........................

……………………………………………………………………………........................[2]

3. Using Fig. 4.2, suggest why a radioactive source which emits 20-MeV alpha-

particles would have a shorter half-life compared to a source which emits 10-

MeV alpha particles.

………………………………………………………………………………………..........

………………………………………………………………………………………..........

……………………………………………………………………………........................

…………………………………………………………………………….......................[2]

distance from centre of nucleus / 10–15 m

En

erg

y / M

eV

30

20

10

Inside nucleus

outside nucleus

9


For Examiner’s

Use

5 (a) When Uranium-235 nuclei are fissioned by slow moving neutrons, the following reaction takes place:

cbYInU 10239

13153

10

23592

Identify the particle c and state the number b of such particles produced in the reaction.

b = ………………… [1]

c = ………………… [1]

(b) The binding energy per nucleon of U-235, I-131 and Y-102 are 7.6 MeV, 8.5 MeV and 8.6 MeV respectively. Calculate the energy released by 1.0 kg of Uranium.

energy released = ………………… J [3]

(c) In all nuclear plants, radioactive wastes are being produced. One of the radioactive

wastes Iodine-131( I13153 ) decays spontaneously with a half-life of 8.02 days.

(i) Calculate the decay constant for Iodine-131.

decay constant = ………………… s-1 [2]

(ii) Another radioactive product Strontium-90 ( Sr90

38 ) has a half-life of 28.8 years.

Explain why I13153 and Sr90

38 were among the most hazardous isotopes.

…………………………………………………………………………………………...........

…………………………………………………………………………………………...........

…………………………………………………………………………………………...........

……………………………………………………………………………....................... [2]

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6 (a) Mobility of charge carriers in a metallic conductor refers to the ease which the charge carriers are able to move through the conductor. Suggest why the charge mobility is inversely related to the resistivity of the conductor.

………………………………………………………………………………………........................

………………………………………………………………………………………........................

……………………………………………………………………………............................... [1]

(b) A sample of silicon is doped with small amount of impurities such as boron or phosphorus which will easily give rise to holes or electrons respectively as majority charge carriers. These impurities are also known as dopants. Fig. 6.1 shows the mobility of the electrons and holes with respect to doping density.

Figure 6.2 shows how the resistivity of an extrinsic semiconductor varies with the doping density.

100

10

1

0.1

0.01

0.001 1014 1016 1018 Fig.

6.5

n-type

p-type

Fig. 6.1

1014 1016 1018 1020

Fig. 6.2

1020

Doping density / cm3

Mo

bili

ty /

cm

2 V

1 s

1

Re

sist

ivity

/

cm

Doping density / cm3

11


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Use

(i) A n-type semiconductor has a cross-sectional area of 0.25 cm2. Using Fig. 6.1 and Fig. 6.2, calculate the resistance per unit length when the mobility of the electrons is 1200 cm2 V1 s1.

resistance per unit length = ………………… cm1 [3]

(ii) Using Fig. 6.1 and Fig. 6.2, state how the mobility of the charge carriers and the resistivity of the semiconductors vary as doping density increases.

………………………………………………………………………………………..............

……………………………………………………………………………....................... [1]

(iii) Explain the apparent contradiction between (a) and (b)(ii).

………………………………………………………………………………………..............

………………………………………………………………………………………..............

………………………………………………………………………………………..............

…………………………………………………………………………….............................

……………………………………………………………………………....................... [2]

12


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(c) Fig. 6.3 shows how the conductivity, , of a n-type semiconductor varies with the reciprocal of the temperature, T1. [Conductivity = 1/resistivity]

Fig. 6.4 shows the typical band diagram of a n-type semiconductor. Electrons can transit from either the valence band or the donor level to the conduction band.

(i) Label ‘P’ and ‘R’ beside the arrows shown in Fig. 6.4 to match the regions P and R in Fig. 6.3. [1]

(ii) Explain your answer to (c)(i).

………………………………………………………………………………………..............

………………………………………………………………………………………..............

………………………………………………………………………………………..............

…………………………………………………………………………….............................

……………………………………………………………………………....................... [2]

P

Q

R

Fig. 6.4

Valence Band

Conduction Band

T1/(103 K1)

electron

Fig. 6.3

13


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Use

(d) When a suitable p-type semiconductor is joined with a n-type semiconductor, it is found that it can act as a solar cell. The I-V characteristic is shown in Fig. 6.5.

Fig. 6.6 shows a magnified version of curve in Fig. 6.5 indicating a particular light level irradiating onto the solar cell.

(i) Estimate the maximum power obtainable from the solar cell using Fig. 6.6.

maximum power = …………………….. W [2]

Fig. 6.6

I/A

V/ V

Fig. 6.5

Voltage / V

Cu

rre

nt /

A

Fig. 6.5

14


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(ii) Discuss if the estimated value in (d)(i) is equal to the maximum power irradiated by the sun onto the solar cell.

………………………………………………………………………………………..............

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………………………………………………………………………………………..............

…………………………………………………………………………….............................

……………………………………………………………………………....................... [3]

~ END OF PAPER 2 ~


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Candidate Name ………………………………. CTG ……….…



28 August 2009 Paper 3 Friday

2 hours

INSTRUCTIONS TO CANDIDATES Write your name and CTG in the spaces at the top of this page. Answer all questions. Write your answers in the spaces provided on the question paper. For numerical answers, all working should be shown clearly. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question.


For Examiner’s Use

Section A

1 /9

2 /9

3 /12

4 /10

Section B

5 /20

6 /20

7 /20

Penalty

Total /80

Candidates answer on the Question Paper. No Additional Materials are required.

2


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Use

[Turn over


permeability of free space, o = 4 10–7 H m–1

permittivity of free space, o = 8.85 10–12 F m–1

(1/(36)) 10–9 F m–1


the Planck constant, h = 6.63 10–34 J s

unified atomic mass constant, u = 1.66 10–27 kg

rest mass of electron, me = 9.11 10–31 kg

rest mass of proton, mp = 1.67 10–27 kg

molar gas constant, R = 8.31 J K–1 mol–1


the Boltzmann constant, k = 1.38 10–23 J K–1

gravitational constant, G = 6.67 10–11 N m2 kg–2

acceleration of free fall, g = 9.81 m s–2

Formulae


1at2

v2 = u2 + 2as

work done on/by a gas, W = pV

hydrostatic pressure, p = g h

gravitational potential,

r

Gm

Displacement of particle in s.h.m. x = xo sin t

velocity of particle in s.h.m., v = vo cos t

= )( 22 xxo



R

1

........

11

21

RR

electric potential,

r

Q

o4



where k = 2

2 )(8

h

EUm


decay constant, = 2

1

6930

t

.

=

=

V =

3


For Examiner’s

Use

[Turn over

Section A Answer all the questions in this section.

1 (a) State the base units associated with upthrust.

base units = …………………........ [1]

(b) A block of copper is suspended in air from an inelastic cord. The tension, T, in the cord is

measured using a force gauge as shown in Fig. 1.1. The copper block is next submerged

fully into a beaker of seawater (see Fig. 1.2). The new measurement of the tension from

the gauge is T.

(i) Suggest a reasonable value of the density of sea water.

density = ………………… kg m-3 [1]

(ii) Explain why T is greater than T.

……………………………………………………………………………....................... [1]

(iii) The densities of the copper block and the seawater are c and s respectively. The

volume of the block is V. Derive an expression for the tension T in terms of c, s

and V.

[2]

Gauge

Copper Block

Fig. 1.1

Gauge

Fig. 1.2

Beaker of seawater

Cord

4


For Examiner’s

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[Turn over

(iv) Hence, deduce how the volume of the block can be estimated using the force

measurements from the set-up in Fig. 1.1 and Fig. 1.2.

……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…… [2]

(c) An iron block of 200 kg is initially suspended vertically using two identical ropes as shown

in Fig. 1.3. Each cord can withstand a maximum tension of 1100 N. Both cords are

shifted slowly apart so that the angle increases at the same rate (see Fig. 1.4).

Calculate the maximum value of attained before the cords break.

maximum = ……………….. [2]

Iron Block

Fig. 1.3

Ropes

Fig. 1.4

5


For Examiner’s

Use

[Turn over

2 (a) Wave–particle duality is the concept that all matter and energy exhibit both wave-like and

particle-like properties. An electron diffraction tube shown in Fig. 2.1 can be used to show

the wave nature of particles.

Electrons are accelerated from rest at the filament towards the target by a potential

difference of 4500 V.

(i) Calculate the speed of the electrons before they reach the target.

speed = ………………..… m s-1 [2]

(ii) Calculate the wavelength associated with the electrons.

wavelength = …………………… m [2]

Fig. 2.1 Fig. 2.2

6


For Examiner’s

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[Turn over

(iii) When the electrons pass through the graphite target, a diffraction pattern is

observed on the screen as shown in Fig. 2.2. The first-order maximum of the

electron diffraction pattern occurs at an angle of 10 from the straight-through

position.

Calculate the separation of the atoms in the graphite.

separation = …………………… m [2]

(b) State three evidences from the photoelectric effect experiment that can be used to show

the particulate nature of electromagnetic radiation.

…………………………………………………………………………………………....................

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……………………………………………………………………………................................. [3]

7


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[Turn over

3 (a) An electron can be made to undergo uniform circular motion by applying a field.

(i) Sketch on Fig. 3.1 an electric field that enables the electron to move in a circular path. [2]

(ii) Sketch on Fig. 3.2 a magnetic field that enables the electron to move in a circular path. [2]

(b) Kepler’s third law states that the square of period, T2, of any planet orbiting around the

Sun is proportional to the cube of their mean distance, r3, from it.

Kepler’s third law led to the discovery of new planets such as Neptune in 1846.

(i) Derive Kepler’s third law from Newton’s law of gravitation.

[3]

(ii) State an assumption made in deriving the answer to (b)(i).

…………………………………………………………………………………………...........

……………………………………………………………………………........................ [1]

v

Fig. 3.1

v

Fig. 3.2

8


For Examiner’s

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[Turn over

(iii) The Earth is at a distance of 1.50 x 1011 m from the Sun. Calculate the distance of

Neptune from the Sun given that Neptune’s orbital period about the Sun is 165

times that of the Earth.

distance = …………………… m [2]

(iv) State the work done by the gravitational force of the Sun to keep the Earth in orbit.

Explain your answer.

………………………………………………………………………..…………....................

……………………………………………………………………………………..................

……………………………………………………………………………........................ [2]

9


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[Turn over

4 (a) Blue diamond, a stable form of carbon (group IV element), is a naturally occurring p-type

semiconductor which contains some boron atoms (group III element). Explain

qualitatively how this example of p-type doping changes the conduction properties of

carbon.

…………………………………………………………………………………………....................

…………………………………………………………………………………………....................

…………………………………………………………………………………………....................

…………………………………………………………………………………………....................

…………………………………………………………………………………………....................

……………………………………………………………………………................................. [3]

(b) A junction is formed when a p-type and a n-type semiconductor are joined together.

A sinusoidal alternating current (a.c.) source is connected across the p-n junction as

shown in Fig. 4.1.

(i) Explain how the junction acts as a rectifier when the switch in Fig. 4.1 is closed.

……………………………………………………………………………..……....................

…………………………………………………………………………………………...........

…………………………………………………………………………………………...........

…………………………………………………………………………………………...........

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

……………………………………………………………………………........................ [4]

p-type n-type

switch a.c. source

resistor

Fig. 4.1

10


For Examiner’s

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[Turn over

(ii) When the switch is closed, power is supplied from the a.c. source at 60 Hz with a

root-mean-square voltage of 220 V. Draw a graph with labelled axes to represent

the time variation of the potential difference across the resistor. Indicate the peak

voltage and the period on the graph.

[3]

11


For Examiner’s

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[Turn over

Section B Answer two questions in this section.

5 (a) (i) Explain what is meant by the internal energy of a gas.

……………………………………………………………………………………….…….…. ……………………………………………………………………………….....…….…. [2]

(ii) The pressure of ideal gas, p, is related to its density, , by the equation 2

31 cp where 2c is the mean square speed of the molecules.

Show that the internal energy of an ideal gas is directly proportional to its thermodynamic temperature.

[3]

(b) Explain, using the kinetic theory of matter, why

(i) the specific latent heat of vaporisation is higher than the specific latent heat of fusion for the same substance,

……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………….....…….…. [3]

12


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(ii) cooling effect accompanies evaporation.

……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………………….…….…. ……………………………………………………………………………….....…….…. [3]

(c) An engine contains 5.2 10–3 mol of gas at volume 5.0 10–5 m3 and pressure 6.0 105 Pa.

(i) Assuming ideal gas behaviour, calculate the temperature of the gas.

temperature of gas = ……..……….… K [2]

(ii) The gas is then heated at constant volume, raising its temperature by 800 K. This is done by supplying 85 J of energy to the gas.

1. The molar heat capacity, cv, of the gas at constant volume is the energy needed to raise the temperature of unit amount of gas by unit temperature. Calculate cv.

molar heat capacity = ……..……….… J mol–1 K–1 [2]

13


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[Turn over

2. Determine the final pressure of the gas.

final pressure of gas = ……..……….… Pa [2]

(iii) During the power stroke of the engine, the gas expands by doing 62 J of work, while no thermal energy enters or leaves the gas.

1. State the first law of thermodynamics.

……………………………………………………………………………………….…….…. ……………………………………………………………………………….....…….…. [1]

2. By applying the law to this process, calculate the change in the internal energy of the gas during the power stroke.

change in internal energy = ……..……….… J [2]

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6 (a) State the laws of electromagnetic induction.

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………............................... [3]

(b) A magnet is released from rest from the top of a copper pipe as shown in Fig. 6.1.

(i) Explain why the time taken for the magnet to fall is considerably longer than when

the magnet is released from the same height without the copper pipe.

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………........ [3]

Fig. 6.1 retort stand

copper pipe

magnet

h

15


For Examiner’s

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[Turn over

(ii) The copper pipe is replaced by a solenoid as shown in Fig. 6.2. The ends of the

solenoid are connected by a wire.

Explain why the time taken for the magnet to fall is shorter as compared to that

when the copper pipe was used.

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………...............

………………………………………………………………………………………........ [3]

Fig. 6.2 retort stand

connecting wire

magnet solenoid

h

16


For Examiner’s

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[Turn over

(c) For the experiment in (b)(i), the variation with time t of the velocity v of the magnet is

shown in Fig. 6.3.

(i) Define displacement.

………………………………………………………………………………………........................

………………………………………………………………………………………........................

………………………………………………………………………………………........................

……………………………………………………………………………................................. [2]

(ii) State the magnitude of the net force acting on the magnet just before it leaves the

pipe.

……………………………………………………………………………................................. [1]

0.0

1.0

2.0

3.0

4.0

5.0

0.0 0.5 1.0 1.5 2.0 2.5

Fig. 6.3

v / m s –1

t / s

17


For Examiner’s

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[Turn over

(iii) Using Fig. 6.3, estimate the value of h shown in Fig. 6.2.

h = ……..……….… m [2]

(iv) Using Fig. 6.3, sketch on Fig. 6.4, the variation with time t of the displacement s of

the magnet. [3]

Fig. 6.4 0.0 0.5 1.0 1.5 2.0 2.5

s / m

t / s

Fig. 6.4

18


For Examiner’s

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[Turn over

(v) The copper pipe is now placed on the table as shown in Fig. 6.5. The magnet is to

be released from the same height as in (b)(i).

Fig. 6.6 shows a predicted v – t graph for the motion of the magnet.

Discuss, with appropriate calculation why the velocity values of P and Q are

incorrect.

……………………………….………………………………………………........................ ………………………………………………………………………………………............... ……………………………….………………………………………………........................ ………………………………………………………………………………………............... ………………………………………………………………………………………........ [3]

0.0 0.5 1.0 1.5 2.0 2.5

P

Q

Fig. 6.6

v / m s-1

t / s

4.0

0.6

0.47

Fig. 6.5

retort stand

copper pipe

magnet

19


For Examiner’s

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[Turn over

7 (a) Some of the energy levels in atomic hydrogen are shown in Fig. 7.1.

Fig. 7.1

(i) Calculate the minimum wavelength of the radiation that could be emitted from

atomic hydrogen.

wavelength = ………………… m [3]

(ii) Sketch the pattern of the visible line emission spectrum of hydrogen. This takes

place when electrons fall to the -3.40 eV level. Mark the red and violet ends of the

spectrum.

[3]

(b) A considerable amount of light can be obtained by connecting 240 V alternating voltage

across a pickle. The emission spectrum is most intense at wavelengths 589.0 nm and

589.6 nm.

(i) Explain how the existence of electron energy levels in atoms gives rise to emission

line spectra.

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………................................. [3]

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[Turn over

(ii) Fig. 7.2 shows the emission spectra of three different elements. Deduce the

element present in the pickle.

……………………………………………………………………………………….......................

……………………………………………………………………………………….......................

……………………………………………………………………………................................. [2]

Fig. 7.2

21


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[Turn over

(c) On Fig. 7.3, monochromatic light of wavelength 300 nm is irradiated onto an aluminium

target. When the switch is closed, the variable resistor is adjusted to a value of 760 to

obtain zero current on the ammeter.

(i) Determine the potential difference across the 40.0 resistor.

potential difference = ………………… V [2]

(ii) Hence, calculate the threshold frequency of the aluminium target.

frequency = ………………… Hz [3]

A

40.0

3.00 V

Fig. 7.3

light

target switch

22


For Examiner’s

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[Turn over

(iii) The switch is now open in Fig. 7.3. Sketch a graph to show the variation with time

of the photoelectric current for each of the following cases:

1. The intensity of the light source is increased at a constant rate. [2]

2. The frequency of the light source is decreased at a constant rate. [2]

~ END OF PAPER 3 ~

2009 h2 physics - yjc.pdf

Documents

yishun junior college

separate optical mark

avogadro constant

planck constant

boltzmann constant

j k1 gravitational constant

molar gas constant

s1 permeability of free