trial examination 2012 vce physics unit 4 -...

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Trial Examination 2012

VCE Physics Unit 4Written Examination

Question and Answer BookletReading time: 15 minutes

Writing time: 1 hour 30 minutes

Student’s Name: ______________________________

Teacher’s Name: ______________________________

Structure of Booklet

Section Number of questions Number of questions to be answered Number of marks

A Core – Areas of study

1. Electric power 5 5 40

2. Interactions of light and matter 4 4 26

B Detailed studies

1. Synchrotron and its applicationsOR

12 12 24

2. PhotonicsOR

12 12 24

3. Sound 12 12 24

Total 90

Students are permitted to bring into the examination room: pens, pencils, highlighters, erasers, sharpeners, rulers, up to two pages (one A4 sheet) of pre-written notes (typed or handwritten) and onescientific calculator. Students are NOT permitted to bring into the examination room: blank pieces of paper and/or white outliquid/tape.Materials suppliedQuestion and answer booklet of 29 pages. Data sheet.Answer sheet for multiple choice questionsInstructionsDetach the data sheet from the centre of this booklet during reading time.Write your name and your teacher’s name in the space provided on this page and on the answer sheet formultiple-choice questions.Unless otherwise indicated, the diagrams in this booklet are not drawn to scale.All written responses must be in English.

Students are NOT permitted to bring mobile phones and/or any other electronic communication devices into the examination room.

Students are advised that this is a trial examination only and cannot in any way guarantee the content or the format of the 2012 VCE Physics Unit 4 Written Examination.

VCE Physics Unit 4 Trial Examination Question and Answer Booklet

2 TEVPHYU4_QA_2012.FM Copyright © 2012 Neap

SECTION A

Areas of study Page

Electric power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Interactions of light and matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Instructions for Section A

Answer all questions for both Areas of study in this section of the paper in the spaces provided. Writeusing black or blue pen.

Where an answer box has a unit printed in it, give your answer in that unit.

You should take the value of g to be

In questions worth more than 1 mark, appropriate working should be shown.

Unless otherwise indicated, diagrams are not to scale.

10 m s 2– .


Copyright © 2012 Neap TEVPHYU4_QA_2012.FM 3

Area of study 1 – Electric power

Question 1

Figure 1 shows an electromagnet and some of its associated magnetic field lines. Two points P and Q are shown on the diagram.

Figure 1

a. Which of the points P or Q represents the North end of the electromagnet?

b. An identical electromagnet with the same current in it is placed next to the first electromagnet as shown in Figure 2.

Figure 2

Which one of the following best represents what happens to the two electromagnets as shown in Figure 2?A. They attract each otherB. They repel each otherC. There is no force acting between them

1 mark

2 marks

P Q

I I

I I I I



Question 2

Eighteen 10 W globes connected to the 240 V AC RMS mains supply are set up in the circuit as shown in Figure 3. One of the globes is labelled G. Each globe is operating at 10 W.

Figure 3

a. Calculate the RMS current through globe G. Show your working.

b. Calculate the resistance of globe G. Show your working.

c. Calculate the RMS current being drawn from the mains. Show your working.

A 2 marks

Ω 2 marks

A 2 marks

240 V AC RMS

G



d. Globe G fails and no longer works.

Which one of the following best describes what happens to the circuit?A. None of the globes now work.B. The bottom row does not work but the other two rows are brighter than before.C. All of the globes work normally except globe G.

D. The bottom row does not work but the other two rows are the same brightness as before.

Question 3

Figure 4 shows a simplified diagram of a student-built DC motor consisting of 50 coils of wire connected in a rectangular shape (ABCD) to a 12 V DC battery. The total resistance of the coils of wire is . The length of side AB is 8.0 cm and the length of side BC is 10.0 cm. The strength of the magnetic field is 2.0 T. The design incorporates curved magnets.

Figure 4

The switch is closed.

a. Calculate the magnitude of the force acting on side AB.

b. Calculate the magnitude of the force acting on side AD.

2 marks

N 2 marks

N 2 marks

4.0 Ω

switch

N

S

BA

D

DC supply

C



c. Which one of the following best indicates the direction of the force acting on side AD?A. upB. downC. leftD. rightE. into the pageF. out of the pageG. no force

d. Explain what happens to the DC motor when the switch is closed.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________2 marks

e. The student-built DC motor does not work properly.

Suggest a method by which the student-built DC motor could be made to work properly.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________2 marks

f. The DC motor shown in Figure 4 has curved magnets.

Explain the purpose of the curved magnets in a DC motor.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________2 marks

2 marks



Question 4

Figure 5 shows a schematic diagram of a direct current (DC) generator. It is being rotated at 10 Hz. The strength of the magnetic field B between the poles is 2.0 T and the area of the coil is 1.0 m

2. The coil is

initially parallel to the magnetic field. The coil has 100 turns in it.

Figure 5

a. Calculate the magnetic flux ΦB through the loop when it has turned through exactly one quarter of a

rotation after the instant shown in Figure 5. Show working and give a unit in your answer.

b. Calculate the magnitude of the average emf generated by the generator in one quarter of a revolution.

3 marks

kV 2 marks

N S

+ –

commutator



c. A cathode ray oscilloscope (CRO) is attached to the output of the commutator.

Which of the following graphs best depicts the voltage variation of the generator?

The commutator in Figure 5 is replaced with two slip rings.

d. Which of the graphs (A–D) above best depicts the voltage variation of the generator with two slip rings?

A. B.

C. D.

2 marks

2 marks

V

t0

V

t0

V

t0

V

t0



Question 5

Scientists studying Emperor penguins during 22 hour long nights in the Antarctic need a power source for their lighting system. To minimise the noise they use a 250 V AC 10 kW generator which is placed 400 m away from the lighting system (Figure 6). The total resistance of the two transmission wires between the generator and the lighting system is .

Figure 6

a. Calculate the current in the transmission wires. Show your working.

b. Calculate the power lost in the transmission lines. Show your working.

c. Calculate the voltage available at the lighting system. Show your working.

A 2 marks

W 2 marks

V 2 marks

2.0 Ω

400 m

250 V generator lighting system



d. The scientists note that there is not enough light produced by the lighting system to study the penguins properly. They have no transformers available but have another 2.4 km of the same type of wire that was used in the transmission lines available.

Explain how they can obtain more power at the lighting system. Support your answer with calculations.

2 marks

END OF AREA OF STUDY 1



Area of study 2 – Interactions of light and matter

Question 1

An unknown metal is used to investigate the photoelectric effect. During the experiment, it is found that the minimum frequency of light which causes electrons to be ejected from the metal surface is Hz.

a. Calculate the work function of the unknown metal.

b. Calculate the maximum velocity of an electron ejected from the unknown metal if light of frequency

Hz is incident on it.

c. If the intensity of the incident light was decreased but the frequency remained the same

( Hz), which of the following would occur?

A. The number of photoelectrons ejected per second would decrease and their maximum velocity would decrease.

B. The number of photoelectrons ejected per second would remain the same and their maximum velocity would decrease.

C. The number of photoelectrons ejected per second would decrease and their maximum velocity would remain the same.

D. The number of photoelectrons ejected per second would remain the same and their maximum velocity would remain the same.

eV 2 marks

m s–1 4 marks

2 marks

4.0 1014×

6.0 1014×

6.0 1014×



d. Explain how the observation, that below the threshold frequency no photoelectrons can be ejected from the metal, can be used as evidence for the particle nature of light.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________3 marks

Question 2

Thomas Young’s famous double slit experiment provided evidence for the wave-like nature of light. To replicate the experiment, laser light of wavelength 700 nm is passed through two narrow slits as shown below.

Figure 1

The distance between the slits and the photographic plate is 1.0 m.

a. At a particular point P on the interference pattern produced on the photographic plate, the path

difference PS2–PS1 is equal to m.

Mark point P on Figure 1 and explain how you chose this point.

________________________________________________________________________________

________________________________________________________________________________

________________________________________________________________________________3 marks

1.0 m

photographic plate

central bright band

slit S1 slit S2

laser

1.75 10 6–×



b. If the wavelength of the laser light is now increased, which of the following would occur?A. The bright and dark bands would both get narrower.B. The bright and dark bands would both get wider.C. The bright bands would get wider and the dark bands would get narrower.

D. The bright bands would get narrower and the dark bands would get wider.

c. Calculate the momentum of a photon with wavelength 700 nm.

d. Young modified his experiment by reducing the intensity of the incident light so that only one photon was between the slits and the photographic plate at a time, and was still able to produce an interference pattern.

Explain how this modification provided confirmation of the wave particle duality of light.

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________2 marks

Question 3

An X-ray beam is passed through a crystal and produces a diffraction pattern as shown in Figure 2.

Figure 2

A similar pattern is then produced by passing an electron beam through the same crystal.

The electrons required to produce the same diffraction pattern as the X-rays would have (one or more answers)A. the same momentum as the X-rays.B. the same energy as the X-rays.C. the same wavelength as the X-rays.D. the same velocity as the X-rays.

2 marks

kg m s–1 2 marks

2 marks



Question 4

Atomic mercury has energy levels as shown in Figure 3 below.

Figure 3

a. Calculate the longest wavelength photon which could cause a mercury atom, initially in the ground state, to be ionised.

b. On Figure 3, draw the electron transition between energy levels which would produce light of

frequency Hz to be emitted from the mercury atom.

2 marks

END OF AREA OF STUDY 2

m 2 marks

E(eV)n = ∞

n = 4

n = 3

n = 2

n = 1

0

–1.6

–3.7

–5.5

–10.4

5.1 1014×



SECTION B – Detailed studies

Detailed study Page

Synchrotron and its applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Photonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Instructions for Section BSelect one Detailed study. Answer all the questions from the Detailed study, in pencil, on the answer sheet provided for multiple-choice questions.Write the name of your chosen Detailed study on the multiple-choice answer sheet and shade thematching box.Choose the response that is correct for the question.A correct answer scores 2, an incorrect answer scores 0.Marks will not be deducted for incorrect answers.No marks will be given if more than one answer is completed for any question.You should take the value of g to be Unless indicated, diagrams are not to scale.

10 m s 2– .



Detailed study 1 – Synchrotron and its applications

The diagram in Figure 1 shows some of the components of the Australian Synchrotron, labelled 1–4.

Figure 1

Question 1

The correct name for the components labelled 1–4 in Figure 1 are

Question 2

The majority of the synchrotron radiation is produced in theA. linac.B. storage ring.C. booster ring.D. beamline.

Component 1 Component 2 Component 3 Component 4

A. linac storage ring booster ring beamline

B. beamline booster ring storage ring linac

C. linac booster ring storage ring beamline

D. beamline storage ring booster ring linac

24

13



An electron gun consists of a heated filament of wire and two plates, X and Y, which are 20 cm apart, as shown in Figure 2.

Figure 2

The acceleration of the electron between the two plates is found to be m s–2.

Question 3

The force on the electron as it travels between the plates is equal toA. N

B. N

C. N

D. N

Question 4

To produce the acceleration of m s–2

, the potential difference between plates X and Y must be equal toA. V

B. V

C. V

D. V

Question 5

The speed of the electron when it reaches plate Y (assuming it was at rest at plate X) is equal toA. m s–1

B. m s–1

C. m s–1

D. m s–1

Filament

plate X plate Y

e

20 cm

1.32 1015×

1.9 10 34–×1.2 10 15–×4.6 103×1.3 1015×

1.32 1015×

2.4 10 16–×1.5 103×1.5 105×1.6 1033×

2.4 10 16–×7.3 106×2.3 107×3.0 108×



An electron is travelling to the right at m s–1 when it enters a region of uniform magnetic field

with magnitude T, and is deflected is a circular path as shown in Figure 3.

Figure 3

Question 6

The direction of the uniform magnetic field is

A. into the page.

B. out of the page.

C. up the page.

D. to the left of the page.

Question 7

The radius of the circular path taken by the electron is equal toA. m

B. m

C. m

D. m

Question 8

If instead of moving in a curved path as shown in Figure 3, the electron entered the uniform magnetic field and continued to travel in a straight line, the magnetic field direction could beA. into the page.

B. out of the page.

C. up the page.

D. to the left of the page.

Question 9

The purpose of an undulator in the storage ring is toA. increase the energy of electrons.B. increase the number of electrons.C. maintain the speed of electrons.D. rapidly change the direction of electrons.

5.0 107×

2.0 10 3–×

electron path

uniform magnetic field

2.3 10 22–×0.14

7.0

4.4 1021×



A crystal of lithium chloride is bombarded with X-rays of wavelength m and Bragg Diffraction occurs. A second order maxima is detected at an angle of 17°.

Question 10

The spacing between the adjacent layers of ions in the lithium chloride crystal is equal toA. m

B. m

C. m

D. m

Question 11

Other maxima could be detected at which of the following pairs of angles?

A. and

B. and

C. and

D. and

Question 12

Incident X-ray photons of energy 1.5 keV strike an electron and undergo Compton scattering.

Which of the following wavelengths could the scattered photons possibly have after the collision?

A. m

B. m

C. m

D. m

END OF DETAILED STUDY 1

1.5 10 10–×

8.8 10 12–×2.6 10 10–×5.1 10 10–×1.0 10 9–×

5.7° 26.2°

8.5° 26.2°

8.5° 34.0°

5.7° 36°

1.9 10 10–×

4.2 10 10–×

8.3 10 10–×

1.1 10 9–×



Detailed study 2 – Photonics

Question 1

Which one of the following particular light sources is most likely to produce coherent light?A. an incandescent light bulbB. a laserC. the sunD. an LED

Question 2

Which one of the following particular light sources is most likely to produce monochromatic light?A. an incandescent light bulbB. the moonC. a laserD. an LED

Figure 1 shows the spectral graph for a blue LED.

Figure 1

Question 3

Which of the following best explains how a blue LED produces its light?A. spontaneous emission of electronsB. spontaneous emission of photonsC. spontaneous absorption of electronsD. spontaneous absorption of photons

Question 4

The blue LED is manufactured to produce light of peak wavelength 435 nm.

The energy gap for this blue LED is closest toA. 1.82 eVB. 1.98 eVC. 2.68 eVD. 2.86 eV

380 480 580 680 780

0.5

1.0

453 nm blue

(nm)



Figure 2 shows a voltage current characteristic graph for a LED.

Figure 2

The LED is placed in a circuit as shown in Figure 3. It shines with a brightness of L mW when the current through the LED is 20 mA.

Figure 3

Question 5

When the current through the LED is 20 mA the resistance of the resistor R is closest to which of the following values?

A.

B.

C.

D.

2 V

voltage

current

breakdown

20 mA

R

LED6.0 V

20 Ω

100 Ω

200 Ω

300 Ω



Question 6

Another identical LED is placed in series with the first LED as shown in Figure 4.

Figure 4

Which one of the following statements best describes the effect of this change?A. Both LEDs will work but each one will shine less than L mW.B. Both LEDs will work and each one will shine with L mW.C. Neither LED will now work.D. There is not enough information to determine what happens to each LED.

Figure 5 shows a schematic diagram of an optic fibre. The refractive index of the cladding is 1.37 and the refractive index of the core is 1.41.

Figure 5

Question 7

Which one of the following is the best description of the optic fibre shown in Figure 5?A. an intensity-based fibreB. a graded-index fibreC. an optic wave guide fibreD. a stepped-index fibre

Question 8

The critical angle for the optic fibre shown in Figure 5 is closest toA. 68.8°B. 76.3°C. 78.7°D. 88.4°

R

LED

LED6.0 V

cladding

core

not to scale



Question 9

The acceptance angle for the optic fibre shown in Figure 5 is closest toA. 6.38°B. 7.95°C. 11.2°D. 19.5°

An optical fibre loses half of its signal strength for every 2.0 km travelled along the optical pipe.

Question 10

This process is best calledA. attenuationB. gainC. refractionD. total internal reflection

Question 11

If the original signal is 40µW the signal at a distance 5.0 km down the optical pipe will be closest toA. 5 µWB. 7 µWC. 10 µWD. 200 µW



Figure 6 shows two different types of optical fibres, P and Q.

Figure 6

Question 12

Which of the following is the best description for these two optical fibres P and Q?A. P is graded-index single mode fibre and Q is a step-index single mode fibre.

B. P is step-index single mode fibre and Q is a graded-index single mode fibre.

C. P is graded-index multimode fibre and Q is a step-index multimode fibre.

D. P is step-index multimode fibre and Q is a graded-index multimode fibre.

END OF DETAILED STUDY 2

P

Q



Detailed study 3 – Sound

Figure 1 shows a dynamic loudspeaker which is producing a 550 Hz sound. Point P is directly in front of the speaker and the speed of sound is 330 m s

–1.

Figure 1

Question 1

Which of the following best describes the motion of a particle at point P due to the sound produced by the speaker?A. The particle is travelling to the right at 330 m s–1.B. The particle is oscillating left and right 550 times per second.C. The particle is oscillating up and down 550 times per second.D. The particle is oscillating left and right at a speed of 330 m s–1.

Question 2

The wavelength of the sound produced by the speaker in Figure 1 is equal toA. mB. mC. mD. m

At point P, the intensity of the sound is W m–2.

Question 3

The sound intensity level (in dB) of the sound at point P is equal toA. dBB. dBC. dBD. dB

Question 4

If the power of the sound produced by the speaker is reduced so that the intensity of the sound at point P

(in W m–2

) decreases to one quarter of its original value, the sound intensity level in dB at point P will be

A. half of its original value.B. one quarter of its original value.C. 3 dB less than its original value.D. 6 dB less than its original value.

P

loudspeaker

0.61.72201.8 105×

2.5 10 7–×

5.454662.5 10 5–×



Question 5

A dynamic loudspeaker operates due to which of the following principles?

A. electrostaticsB. capacitanceC. resonanceD. electromagnetism

Loudspeakers are usually encased in a baffle which contains carefully placed ports (holes) through the baffle.

Question 6

Which of the following suggests the correct purpose for the baffle and ports?

Baffle Port

A. eliminate destructive interference between the front and the back of the speaker

allow sound from the front and back of the speaker to be added constructively for low frequencies

B. eliminate destructive interference between the front and the back of the speaker

prevent sound from the front and back of the speaker to be added constructively for low frequencies

C. eliminate constructive interference between the front and the back of the speaker

allow sound from the front and back of the speaker to be added constructively for low frequencies

D. eliminate constructive interference between the front and the back of the speaker

prevent sound from the front and back of the speaker to be added constructively for low frequencies



A clarinet can be modelled as a 0.7 m long pipe closed at one end, as shown in Figure 2. The speed of sound

inside the pipe is 336 m s–1

.

Figure 2

The clarinet is played so that it produces a sound of frequency 360 Hz.

Question 7

The frequency of 360 Hz isA. the fundamental frequency for this pipe.B. the first overtone for this pipe.C. the second harmonic for this pipe.D. the second overtone for this pipe.

Question 8

Which of the following frequencies could also be produced by this pipe?A. 60 HzB. 120 HzC. 480 HzD. 720 Hz

Question 9

Which of the following diagrams correctly represents the pressure variation for the clarinet when the second overtone is produced?

A. B.

C. D.

0.7 m

0.7 m 0.7 m

0.7 m 0.7 m



Question 10

Which of the following correctly describes the principle on which the electret-condenser, crystal and velocity microphones operate?

Question 11

A music practice room has a sliding door which can be opened or closed by different amounts, with a maximum opening width of 1.5 m. A pianist is practising in the practice room and is located at position X. Erin is outside in the corridor at position Y, as shown in Figure 3. Assume that the piano produces all notes with equal intensity. The speed of sound is equal to 340 m s

–1.

Figure 3

Which of the following combinations of piano note frequency and doorway opening width would sound the loudest to Erin?

Electret-condenser microphone

Crystal microphone Velocity microphone

A. capacitance electromagnetism piezo-electric effect

B. piezo-electric effect electromagnetism capacitance

C. electromagnetism capacitance piezo-electric effect

D. capacitance piezo-electric effect electromagnetism

Frequency of piano note Width of open doorway

A. 300 Hz 0.5 m

B. 1000 Hz 0.5m

C. 300 Hz 1.5 m

D. 1000 Hz 1.5 m

corridorErinposition Y

doorway

pianistposition X



Question 12

The graph shown in Figure 4 indicates the sensitivity of the average human ear to different frequency sounds.

Figure 4

Question 12

The graph in Figure 4 shoes that a person with average hearing perceives a 1000 Hz sound at 40 dB to beA. equally loud as a 1000 Hz sound at 80 dB.B. quieter than a 100 Hz sound at 40 dB.C. equally loud as a 10 000 dB sound at 60 dB.D. louder than a 2000 Hz sound at 40 dB.

END OF QUESTION AND ANSWER BOOKLET

120

100

80

60

40

20

0

100 1000 20005002005020

0

20

40

60

80

100

120

frequency (Hz)

soun

d le

vel

threshold of hearing

5K 10K 20K

trial examination 2012 vce physics unit 4 -...

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