Cambridge A Level Physics 9702 — 2005 Oct/Nov Paper 6 · Variant 1

This document consists of 20 printed pages. SP (CW/AR) S74758/2 © UCLES 2005 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level PHYSICS 9702/06 Paper 6 October/November 2005 45 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen in the spaces provided on the Question Paper. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all of the questions in any two options. You may use a soft pencil for any diagrams, graphs or rough working. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. Centre Number Candidate Number Name For Examiner’s Use A F M P T Total

2 9702/06/O/N/05 Data speed of light in free space, c = 3.00 × 108 m s–1 permeability of free space,
0 = 4 × 10–7 H m–1 permittivity of free space, 0 = 8.85 × 10–12 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 © UCLES 2005

3 9702/06/O/N/05 [Turn over Formulae uniformly accelerated motion, s = ut +
 at 2 v2 = u2 + 2as work done on/by a gas, W = pV gravitational potential, φ = – simple harmonic motion, a = –
2x velocity of particle in s.h.m., v = v0 cos
t v = ±
√(x2 0 – x2) resistors in series, R = R1 + R2 + . . . resistors in parallel, 1/R = 1/R1 + 1/R2 + . . . electric potential, V = capacitors in series, 1/C = 1/C1 + 1/C2 + . . . capacitors in parallel, C = C1 + C2 + . . . energy of charged capacitor, W =
 QV alternating current/voltage, x = x0 sin
t hydrostatic pressure, p = qgh pressure of an ideal gas, p =
 <c2> radioactive decay, x = x0 exp(– t) decay constant,  = critical density of matter in the Universe, q0 = equation of continuity, Av = constant Bernoulli equation (simplified), p1 +
 qv2 1 = p2 +
 qv2 2 Stokes’ law, F = Arv Reynolds’ number, Re = drag force in turbulent flow, F = Br2qv2 qvr  3H0 2 8G 0.693 t
 Nm V Q 40r Gm r © UCLES 2005

4 9702/06/O/N/05 Answer all of the questions in any two of the Options. Answer the questions in the spaces provided on the Question Paper. The Options are as follows. Option A Astrophysics and Cosmology questions 1, 2 and 3 Option F The Physics of Fluids questions 4, 5 and 6 Option M Medical Physics questions 7, 8 and 9 Option P Environmental Physics questions 10, 11 and 12 Option T Telecommunications questions 13, 14 and 15 Option A Astrophysics and Cosmology 1 (a) Define (i) the astronomical unit (AU), … …[1] (ii) the parsec (pc). … … …[2] (b) Calculate the magnitude, in metres, of the parsec given that 1.0 AU = 1.5 ×1011m. 1.0 parsec = … m [3] For Examiner’s Use © UCLES 2005

5 9702/06/O/N/05 [Turn over 2 One model of the Universe is based on the ‘hot big bang’ and another is based on the ‘infinite and static’ concept. (a) State two pieces of experimental evidence in support of a ‘hot big bang’ model. 1. … … 2. … …[2] (b) State Olbers’ paradox. … … … …[3] (c) Explain why the ‘hot big bang’ model does not necessarily imply that the Universe will expand indefinitely. … … … …[3] For Examiner’s Use © UCLES 2005

6 9702/06/O/N/05 3 A telescope that will detect infra-red radiation has recently been put into Earth-orbit. (a) State two reasons why such a telescope is likely to operate more successfully in Earth- orbit than on the Earth’s surface. 1. … … 2. … …[2] (b) Suggest, with a reason in each case, two types of object that are likely to be observed more effectively in the infra-red region of the spectrum than in the visible region. 1. … … … 2. … … …[4] For Examiner’s Use © UCLES 2005

7 9702/06/O/N/05 [Turn over Option F The Physics of Fluids 4 The Bernoulli equation for fluid flow may be expressed in the form p1 + ¹⁄₂ρv1 2 = p2 + ¹⁄₂ρv2 2. (a) State three conditions for this equation to apply. 1. … … 2. … … 3. … …[3] (b) An aerofoil has an effective area of 25 m2. Air of density 1.2 kg m–3 flows over the aerofoil at a speed of 85 m s–1 and under the aerofoil at 75 m s–1. Calculate the lift force on the aerofoil. lift force = … N [3] For Examiner’s Use © UCLES 2005

8 9702/06/O/N/05 5 A glass tube of uniform cross-sectional area is sealed at one end and contains some sand. The tube floats upright in water as illustrated in Fig. 5.1. Fig. 5.1 The centre of mass of the tube and its contents is at C. (a) (i) State what is meant by the centre of buoyancy. … …[1] (ii) On Fig. 5.1, mark the position of the centre of buoyancy of the floating tube. Label this point B. [1] (iii) The tube is displaced slightly from the vertical. Explain why the tube returns to the vertical position when released. … … … …[3] C water surface sand tube For Examiner’s Use © UCLES 2005

9 9702/06/O/N/05 [Turn over (b) Sand is gradually removed from the tube. State what change, if any, occurs in (i) the depth of immersion of the tube, …[1] (ii) the distance between the base of the tube and the centre of buoyancy B, …[1] (iii) the distance between the base of the tube and the centre of mass C of the tube and its contents. …[1] (c) For one particular mass of sand in the tube, the tube no longer stays floating vertically. State and explain the relative positions of C and of B for this to occur. … … …[2] For Examiner’s Use © UCLES 2005

10 9702/06/O/N/05 6 (a) State what is meant by turbulent flow. … …[1] (b) By reference to energy principles, explain why an increase in turbulence behind a car will increase the drag force on the car. … … … …[3] For Examiner’s Use © UCLES 2005

11 9702/06/O/N/05 [Turn over Option M Medical Physics 7 (a) Outline the principles of production of X-rays in an X-ray tube. The detailed structure and operation of an X-ray tube are not required. … … … … … … … … …[6] (b) The quality of the image on an X-ray plate depends on the sharpness and on the contrast. Explain what is meant by (i) sharpness, … …[1] (ii) contrast. … …[1] For Examiner’s Use © UCLES 2005

12 9702/06/O/N/05 8 Fig. 8.1 shows parallel rays of light refracted by a defective eye. Fig. 8.1 It is assumed that all the refraction of the light takes place at the front surface of the eye. (a) State the defect of this eye. …[1] (b) (i) In position AB on Fig. 8.2, draw a lens that could be used to correct the defect. [1] Fig. 8.2 (ii) Complete Fig. 8.2 by drawing the light rays through the lens and into the eye. [2] A B For Examiner’s Use © UCLES 2005

13 9702/06/O/N/05 [Turn over 9 (a) (i) Distinguish between the intensity of a sound consisting of one frequency and its loudness. … … … …[2] (ii) State what is meant by the sensitivity of the ear. … …[1] (b) The minimum change in intensity level (I.L.) that can be detected by a certain person is 3 dB when the intensity level is 89 dB. Calculate the ratio intensity of sound at intensity level 89 dB ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– increase in intensity corresponding to 3 dB increase in intensity level at 89 dB ratio = … [5] For Examiner’s Use © UCLES 2005

14 9702/06/O/N/05 Option P Environmental Physics 10 (a) Draw a labelled diagram to show the main features of a solar panel. [3] (b) Suggest why, when installing a solar panel in the southern hemisphere, the panel should face northwards at noon. … …[1] For Examiner’s Use © UCLES 2005

15 9702/06/O/N/05 [Turn over (c) Fig. 10.1 shows the variation with time of the Sun’s power incident per unit area of the Earth’s surface at one position in the southern hemisphere. Fig. 10.1 A solar panel has an area of 1.4 m2 and is to be used to raise the temperature of water by a minimum of 15 K. The efficiency of energy collection by the panel is 35% and the specific heat capacity of water is 4200 J kg–1K–1. Use data from Fig. 10.1 to determine the maximum rate of flow of water through the panel so that the water may be heated for six hours each day. rate of flow = … kg s–1 [3] 0 200 400 600 800 1000 0600 0900 noon 1500 1800 time power per unit area / W m–2 For Examiner’s Use © UCLES 2005

16 9702/06/O/N/05 11 (a) (i) State what is meant by an adiabatic change. … … …[2] (ii) Suggest why, during the compression stroke of a petrol engine, the change is said to be adiabatic. … … …[2] (b) Fig. 11.1 represents one cycle of a four-stroke petrol engine. Fig. 11.1 On Fig. 11.1, (i) mark with arrows the direction of the changes in the cycle, [1] (ii) label with the letter E the section of the cycle during which the fuel is burned. [1] pressure volume For Examiner’s Use © UCLES 2005

17 9702/06/O/N/05 [Turn over 12 (a) Suggest why, in some countries, the use of unleaded fuel, rather than leaded fuel, has been introduced. … … …[2] (b) State two forms of pollution, other than air pollution, associated with the use of cars. 1. … … 2. … …[2] (c) The use of wind generators for the production of electrical energy is said, by some, to be a renewable pollution-free alternative to generation using fossil fuels. (i) Suggest what is meant by renewable. … …[1] (ii) Discuss briefly the respects in which wind turbines can be considered to be ‘pollution-free’. … … … …[2] For Examiner’s Use © UCLES 2005

18 9702/06/O/N/05 Option T Telecommunications 13 (a) Explain what is meant by fibre-optic transmission of a signal. … … … …[3] (b) Give two technological and two social advantages of fibre-optic transmission when compared with metal cable transmission. technological 1. … … 2. … … social 1. … … 2. … …[4] For Examiner’s Use © UCLES 2005

19 9702/06/O/N/05 [Turn over 14 The input signal to a metal cable of length 75 m has a power of 0.60 W. The output signal from the cable is 0.55 W. (a) (i) Suggest the main cause of this loss of power (attenuation) in the cable. … …[1] (ii) Calculate the signal attenuation, in dB km–1, of the metal cable. attenuation = … dB km–1 [4] (b) The maximum uninterrupted length of cable for the transmission of a signal is limited not only by attenuation but also by noise. (i) Explain what is meant by noise. … …[1] (ii) Suggest two sources of noise in metal cables. 1. … … 2. … …[2] For Examiner’s Use © UCLES 2005

20 9702/06/O/N/05 15 Discuss briefly the effects on society of the change to the transmission of signals in digital, rather than analogue, form. … … … … … … … … … …[5] For Examiner’s Use © UCLES 2005 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Level MARK SCHEME for the November 2005 question paper 9702 PHYSICS 9702/06 Options maximum raw mark 40 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the November 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 1 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9702 6 © University of Cambridge International Examinations 2005 Option A - Astrophysics and Cosmology 1 (a) (i) (mean) distance between Earth and Sun B1 [1] (ii) distance at which 1 AU subtends an angle M1 of one arc-second A1 [2] (b) arc = rθ C1 1.5 × 1011 = r × 2π / (360 × 60 × 60) M1 1.0 pc = 3.09 × 1016 m A1 [3] 2 (a) e.g. 3 K microwave background radiation redshift of light from galaxies any two sensible suggestions, 1 each, max 2 B2 [2] (b) If Universe is static and infinite B1 then every line of sight would end on a star M1 so night would be as bright as day A1 [3] (c) depends on (mean) density of matter in the Universe B1 greater than a certain value, Universe will expand and then contract B1 below this certain value, Universe will expand indefinitely B1 [3] 3 (a) e.g. absorption of IR by water vapour in atmosphere much stray IR at Earth’s surface any two sensible suggestions, 1 each, max 2 B2 [2] (b) e.g. distant galaxies B1 moving so fast that they are red-shifted into IR B1 e.g. cool objects (brown dwarfs) B1 give off IR but not visible light B1 [4] allow any two sensible suggestions (2) + reasoning (1 + 1)

Page 2 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9702 6 © University of Cambridge International Examinations 2005 Option F - The Physics of Fluids 4 (a) e.g. incompressible fluid / constant density horizontal flow non-viscous streamline any three, 1 each, max 3 B3 [3] (b) force = A∆p C1 = 25 × ½ × 1.2 × (852 – 752) C1 = 2.4 × 104 N A1 [3] 5 (a) (i) centre of mass of displaced fluid B1 [1] (ii) B shown at centre of submerged section B1 [1] (iii) upthrust acts upwards through B B1 weight acts downwards through C B1 these two forces provide a restoring couple B1 [3] (b) (i) becomes less B1 [1] (ii) decrease B1 [1] (iii) increases B1 [1] (c) C and B coincide M1 no longer providing a restoring couple A1 [2] 6 (a) non-steady / haphazard flow of fluid B1 [1] (b) turbulence represents (continuous) transfer of kinetic energy B1 this transfer of energy per unit time represents power B1 power = FD × speed so more power means larger FD B1 [3]

Page 3 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9702 6 © University of Cambridge International Examinations 2005 Option M - Medical Physics 7 (a) electrons accelerated / high speed electrons B1 bombard metal target B1 electrons decelerated greatly → e.m. radiation B1 wide range of decelerations gives continuous spectrum B1 electrons in target atoms excited B1 de-excitation of these electrons gives line spectrum B1 [6] (b) (i) sharpness: ease with which edges of structures can be seen B1 [1] (ii) contrast: difference in blackening between structures B1 [1] 8 (a) short sight (myopia) B1 [1] (b) (i) concave lens drawn B1 [1] (ii) rays diverge after passing through the concave lens B1 rays converge on the retina B1 [2] 9 (a) (i) intensity: energy per unit area per unit time (normal to area) B1 loudness: subjective response (of a person) to (a given) intensity B1 (ii) ability to distinguish between two different intensities of sound B1 [3] (b) intensity level = 10 lg(I / I0) 89 = 10 lg I / (1.0 × 10–12) C1 I89 = 7.94 × 10–4 W m–2 C1 92= 10 lg I / (1.0 × 10–12) I92 = 1.58 × 10–3 W m–2 C1 ratio = I89 / (I92 – I89) C1 = 1.0 A1 [5]

Page 4 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9702 6 © University of Cambridge International Examinations 2005 Option P - Environmental Physics 10 (a) diagram: closed box with glass top B1 metal base and water tubing B1 blackened interior B1 [3] (b) largest area normal to sunlight B1 [1] (c) power = flow rate × c × ∆θ C1 800 × 0.35 × 1.4 = flow rate × 4200 × 15 C1 flow rate = 6.2 × 10–3 kg s–1 A1 [3] 11 (a) (i) change in pressure and volume (and temperature) M1 without any (thermal) energy entering or leaving the system A1 [2] (ii) the change takes place rapidly B1 no time for energy to flow in/out of the gas B1 [2] (b) (i) correct direction shown (clockwise) B1 [1] (ii) correct section marked (vertical section on left of diagram) B1 [1] 12 (a) the lead compounds are released as air pollution B1 any further comment e.g. cause mental disorders, enter food chain via plants B1 [2] (b) e.g. noise, visual any two sensible suggestions, 1 each, max 2 B2 [2] (c) (i) available without using (fossil) fuels B1 [1] (ii) e.g. do not produce air pollution, no mining/transportation any two sensible suggestions, 1 each, max 2 B2 [2]

Page 5 Mark Scheme Syllabus Paper GCE A LEVEL – November 2005 9702 6 © University of Cambridge International Examinations 2005 Option T - Telecommunications 13 (a) signal is in the form of a series of pulses of light/IR B1 pulses pass along a glass fibre B1 as a result of total internal reflection B1 [3] (b) technological: e.g. greater bandwidth, less noise, less power loss per unit length any two sensible suggestions, 1 each, max 2 B2 social: e.g. increased security, cheaper, less bulky any two sensible suggestions, 1 each, max 2 B2 [4] 14 (a) (i) thermal energy (in the cable) / resistance B1 [1] (ii) loss = 10 lg(0.55 / 0.60) C1 = (-) 0.38 dB C1 loss per unit length = 0.38 / 75 × 10–3 C1 = 5.0 dB km–1 A1 [4] (b) (i) unwanted (random) signal power B1 [1] (ii) e.g. molecular/lattice vibrations, pick-up of e.m. signals any two sensible suggestions, 1 each, max 2 B2 [2] 15 digital more reliable than analogue fewer people employed in telephone industry greater multiplexing means reduced cost per call reduced costs means available to more people huge expansion international calls huge expansion of non-voice communications development/expansion of internet introduction of multichannel cable TV companies any five sensible statements, 1 each, max 5 B5 [5]