Cambridge A Level Physics 9702 — 2005 May/June Paper 6 · Variant 1

This document consists of 21 printed pages and 3 blank pages. SP (CW/AR) S74759/3 © UCLES 2005 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level PHYSICS 9702/06 Paper 6 May/June 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. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all of the questions in any two options. The number of marks is given in brackets [ ] at the end of each question or part question. You may lose marks if you do not show your working or if you do not use appropriate units. Centre Number Candidate Number Name For Examiner’s Use If you have been given a label, look at the details. If any details are incorrect or missing, please fill in your correct details in the space given at the top of this page. Stick your personal label here, if provided. A F M P T Total

2 9702/06/M/J/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/M/J/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/M/J/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 and 14 Option A Astrophysics and Cosmology 1 Fig.1.1 illustrates the Milky Way galaxy. Fig. 1.1 (a) On Fig. 1.1, mark the approximate position of the Solar System. [1] For Examiner’s Use © UCLES 2005

5 9702/06/M/J/05 [Turn over (b) State approximate values, in light-years, for (i) the diameter of the Milky Way galaxy, diameter = … light-years [1] (ii) the average separation of stars in one arm of the galaxy. separation = … light-years [1] (c) Hubble was able to map out the Universe to a distance of approximately 500 million light-years. State the number of galaxies that were estimated to exist within this distance. number = … [1] For Examiner’s Use © UCLES 2005

6 9702/06/M/J/05 2 Fig. 2.1 shows the variation with age of the temperature of the Universe. Fig. 2.1 (a) Point F on the graph represents the point at which light elements were formed. Suggest the maximum temperature at which this formation occurred. temperature = … K [1] (b) Mark the point on the line at which galaxies began to form. [1] (c) Suggest why, in the Universe, there is an excess of matter over antimatter. … … … … …[4] For Examiner’s Use © UCLES 2005 0 100 102 104 106 108 1010 1012 1014 1016 1018 age / s temperature / K F

7 9702/06/M/J/05 [Turn over 3 It has been reported recently that some galaxies have been discovered that are estimated to be 12600 million light-years from Earth. (a) (i) The Hubble constant has been estimated to be 60 km s–1Mpc–1. Use this value to calculate the approximate age of the Universe. (1 pc = 3.1 ×1016m) age = … years [5] (ii) Hence calculate the fraction of the age of the Universe for which the light from these galaxies has been travelling to Earth. fraction = … [1] (iii) Suggest why the discovery of these galaxies may have significance for an understanding of the development of the Universe. … … …[2] (b) Explain why there is a limit to the extent of the observable Universe. … … …[2] For Examiner’s Use © UCLES 2005

8 9702/06/M/J/05 Option F The Physics of Fluids 4 A rectangular iceberg floats in seawater of density 1030 kg m–3, as illustrated in Fig. 4.1. Fig. 4.1 The iceberg floats with its top, area 6.4 ×104m2, 28 m above the surface of the sea. The density of ice is 920 kg m–3. (a) State what provides the upthrust on an object when it is immersed in a fluid. … …[1] (b) The bottom of the iceberg is at a depth d, measured in metres. Give expressions, in terms of d, for (i) the mass of the iceberg, … … …[2] (ii) the mass of seawater displaced by the iceberg. … …[1] surface of sea area of top 6.4 x 104 m2 28 m d For Examiner’s Use © UCLES 2005

9 9702/06/M/J/05 [Turn over (c) Using your answers in (b), determine (i) the depth d, d = … m [2] (ii) the fraction of the iceberg that is below the water surface. fraction = … [1] For Examiner’s Use © UCLES 2005

10 9702/06/M/J/05 5 (a) Explain what is meant by a viscous liquid. … … …[2] (b) Suggest why, for viscous flow of a fluid through a pipe, the flow rate is expressed as a volume flow rate, measured in m3s–1, rather than a linear speed, measured in m s–1. … … …[2] (c) The volume flow rate V of a viscous liquid undergoing steady flow through a tube of length L and radius r is given by V = , where η is the viscosity of the liquid and p is the pressure difference between the ends of the tube. Water of density 1.0 ×103kg m–3 flows out of a container through a tube of length 13 cm and internal diameter 1.8 mm, as illustrated in Fig. 5.1. Fig. 5.1 water tube 13 cm 9.1 cm πr 4p –––– 8ηL For Examiner’s Use © UCLES 2005

11 9702/06/M/J/05 [Turn over When the axis of the tube is at a depth of 9.1 cm below the water surface, water runs out of the tube at a rate V of 1.5 ×10–6m3s–1. (i) Show that the pressure difference between the ends of the tube is approximately 890 Pa. [2] (ii) Determine the viscosity of the water. viscosity = … N s m–2 [2] For Examiner’s Use © UCLES 2005

12 9702/06/M/J/05 6 Streamlines are a means by which fluid flow may be modelled. (a) Explain (i) what is meant by a streamline, … …[1] (ii) why streamlines can never touch or cross. … …[1] (b) State and explain the change in fluid flow when streamlines become closer together. … … … …[3] For Examiner’s Use © UCLES 2005

13 9702/06/M/J/05 [Turn over Option M Medical Physics 7 (a) Outline briefly the use of magnetic resonance to obtain diagnostic information about internal body structures. … … … … … … … … …[5] (b) In some medical applications, the diagnostic information may be obtained using magnetic resonance or using X-rays. State two disadvantages of the use of magnetic resonance. 1. … … 2. … …[2] For Examiner’s Use © UCLES 2005

14 9702/06/M/J/05 8 A person is accidentally exposed for a short time to ionising radiation. (a) Explain (i) what is meant by absorbed dose, … … …[2] (ii) why the effect of the exposure depends on the type of radiation. … … …[2] (b) Suggest why the effects of the exposure cannot be fully assessed within a few weeks of the exposure. … … …[2] For Examiner’s Use © UCLES 2005

15 9702/06/M/J/05 [Turn over 9 A person discovers that the power of the lens used to correct the defect of one of his eyes is +2.5 D. (a) For this corrective lens, (i) name the type of lens, …[1] (ii) calculate the focal length in centimetres. focal length = … cm [1] (b) (i) Name the defect of this eye. …[1] (ii) Make calculations to estimate the distance of the far point and the distance of the near point from this unaided eye. distance of far point = … distance of near point = … [4] For Examiner’s Use © UCLES 2005

16 9702/06/M/J/05 Option P Environmental Physics 10 (a) Explain why the Earth’s resources of fossil fuels are different from the total reserves. … … … …[3] (b) The formation of fossil fuels is a continuous process. Suggest why the reserves of these fuels are considered to be finite. … … …[2] For Examiner’s Use © UCLES 2005

17 9702/06/M/J/05 [Turn over 11 (a) Complete Fig. 11.1 to illustrate the action of a four-stroke petrol engine. [4] Fig. 11.1 (b) Modern four-stroke petrol engines frequently consist of four cylinders, each fitted with two inlet valves and two exhaust valves. Suggest, with one reason (in each case), why (i) there are four cylinders, … … …[2] (ii) there are more than two valves in each cylinder. … … …[2] For Examiner’s Use © UCLES 2005 stroke induction compression power … inlet valve open … … closed outlet valve … … … open

18 9702/06/M/J/05 12 (a) (i) Explain what is meant by pollution. … … …[2] (ii) State one example of pollution that is 1. man-made, … 2. natural. … [2] (b) Suggest why large areas of forest are important to maintain the Earth’s atmosphere and the environment. … … … …[3] For Examiner’s Use © UCLES 2005

19 9702/06/M/J/05 [Turn over Option T Telecommunications 13 An analogue signal is to be transmitted in digital form. (a) Outline briefly the principles involved in the analogue-to-digital conversion of the signal and its transmission. … … … … … … … …[5] (b) Suggest two advantages of the transmission of data in digital form. 1. … … 2. … …[2] For Examiner’s Use © UCLES 2005

20 9702/06/M/J/05 14 It is proposed to install an optic fibre link between London (England) and Sydney (Australia). The optic fibre, length 18000 km, has an attenuation of 1.7 dB km–1. The noise power in the fibre is 6.0 ×10–19W. The refractive index of the core of the fibre is 1.5. (a) Explain what is meant by (i) attenuation, … …[1] (ii) noise. … …[1] (b) The signal-to-noise ratio must not fall below 25 dB. (i) Show that the smallest effective signal power that can be detected in the fibre is 1.9 ×10–16 W. [2] (ii) Calculate the maximum uninterrupted length of fibre through which a signal can be transmitted for an input signal of power 7.0 mW. length = … km [3] For Examiner’s Use © UCLES 2005

21 9702/06/M/J/05 (c) With reference to your answer in (b)(ii), suggest what can be done to enable the signal to be received in Sydney. … …[1] (d) An alternative means by which the signal could be sent is by using a geostationary satellite. The orbit of such a satellite is 3.6 ×104km above the Earth’s surface. (i) Explain what is meant by a geostationary orbit. … … …[2] (ii) By considering the times of transmission by optic fibre and by satellite, explain briefly one advantage of the fibre when compared with the satellite. … …[3] For Examiner’s Use © UCLES 2005

24 9702/06/M/J/05 BLANK PAGE 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 Subsidiary and Advanced Level MARK SCHEME for the June 2005 question paper 9702 PHYSICS 9702/06 Paper 6, maximum mark 40 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. This 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. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Grade thresholds for Syllabus 9702 (Physics) in the June 2005 examination. minimum mark required for grade: maximum mark available A B E Component 6 40 26 23 14 The thresholds (minimum marks) for Grades C and D are normally set by dividing the mark range between the B and the E thresholds into three. For example, if the difference between the B and the E threshold is 24 marks, the C threshold is set 8 marks below the B threshold and the D threshold is set another 8 marks down. If dividing the interval by three results in a fraction of a mark, then the threshold is normally rounded down.

June 2005 GCE A AND AS LEVEL MARK SCHEME MAXIMUM MARK: 40 SYLLABUS/COMPONENT: 9702/06 PHYSICS Paper 6

Page 1 Mark Scheme Syllabus Paper GCE A/AS LEVEL – JUNE 2005 9702 6 © University of Cambridge International Examinations 2005 Option A - Astrophysics and Cosmology 1 (a) position: on a spiral arm, between ½ and ¾ distance from centre B1 [1] (b) (i) allow 80 000 → 150 000 light-years B1 (ii) allow 2 → 10 light-years B1 [2] (c) allow 107 → 109 B1 [1] 2 (a) allow 108 → 1010 K B1 [1] (b) position marked between 1012 s and 1013 s B1 [1] (c) result of X-bosons (allow ‘bosons’) B1 at (very) early stages of development of the Universe B1 (X-) boson decays into quarks M1 (slightly) more slowly than its antiparticle decays A1 [4] 3 (a) (i) H0 = (60 × 103)/(3.1 × 1016 × 106) C1 = 1.9 × 10-18 (s-1) C1 age of Universe = 1/H0 (or clear substitution for H0 shown) B1 = 5.2 × 1017 s C1 = 1.6 × 1010 years A1 [5] (ii) fraction of time = (12600 × 106)/(1.6 × 1010) = 0.79 or 63/80 A1 [1] (iii) light left galaxy when Universe was much younger B1 (so) ‘looking back’ in time B1 [2] (b) limit set by how far light can travel M1 during the lifetime of the Universe A1 or galaxies at very large distances are moving very fast so Doppler shifted out of visible [2] Option F - The Physics of Fluids 4 (a) pressure difference (between upper and lower surfaces) B1 [1] allow ‘upthrust provided by displaced fluid’ (b) (i) mass = density × volume C1 = 920 × 6.4 × 104 × (28 + d) A1 [2] (ii) either 920 × 6.4 × 104 × (28 + d) or 1030 × 6.4 × 104 × d A1 [1] (c) (i) 920 × 6.4 × 104 × (28 + d) = 1030 × 6.4 × 104 × d C1 d = 234 m A1 [2] (ii) fraction = 234/(234 + 28) = 0.89 A1 [1]

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL – JUNE 2005 9702 6 © University of Cambridge International Examinations 2005 5 (a) fluid in which there is internal friction B1 either resisting motion of an object through the fluid or resisting movement between layers of fluid B1 [2] (b) there is no single value for the speed in the pipe B1 (do not allow unqualified ‘constant’) any other comment e.g. volume flow rate takes into account whole flow B1 [2] (c) (i) pressure (= ρgh) = 1.0 × 103 × 9.8 × 9.1 × 10-2 M1 = 890 Pa A0 some explanation as to why this is the pressure difference B1 [2] (ii) 1.5 × 10-6 = (π × {0.9 × 10-3}4 × 890)/(8 × η × 13 × 10-2) C1 η = 1.18 × 10-3 N s m-2 A1 [2] 6 (a) (i) path taken by a particle of the fluid B1 [1] (ii) each particle can follow only one path B1 [1] (or in terms of tangent being direction of motion, and only one direction) (b) (in any tube of flow) Av = constant M1 when lines converge, A becomes smaller A1 (so) v must increase B1 [3] Option M - Medical Physics 7 (a) large/uniform magnetic field applied (to patient) (1) pulse of radio-frequency waves (1) Causes H-atoms in patient to resonate or vibrate at Lamour frequency (1) H-atoms give off radio-frequency waves (1) RF detected and processed (1) to give positions of H-atoms (1) non-uniform magnetic field enables positions of resonating atoms to be defined (1) [1 each, any five] B5 [5] (b) e.g. cost, portability of equipment, time taken [any sensible suggestions, 1 each, max 2] B2 [2] 8 (a) (i) energy deposited in body M1 per unit mass of (body) tissue A1 [2] (ii) effects depend on density of deposition of energy/ionisation B1 some radiations cause greater density of ionisation than others B1 [2] (b) Radiation has long-term effects M1 any other relevant point e.g. life shortening, hereditary, cancer inducing A1 [2] 9 (a) (i) convex/converging B1 [1] (ii) focal length (= 100/2.5) = 40 cm B1 [1] (b) (i) long sight (hypermetropia) B1 [1] (ii) far point is at infinity B1 normal nearpoint is distance 25 cm from eye B1 1/25 - 1/v = 1/40 C1 v = 67 cm nearpoint is 67 cm in front of the eye A1 [4]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – JUNE 2005 9702 6 © University of Cambridge International Examinations 2005 Option P - Environmental Physics 10 (a) resources: total energy available/stored in Earth B1 reserves: total energy that can be extracted (economically) B1 reserves less than resources because some fossil fuels not recoverable/too expensive B1 [3] (b) formation takes place over millions/thousands of years B1 fossil fuels will be exhausted in much less time than this B1 [2] 11 (a) induction compression power EXHAUST open CLOSED CLOSED closed CLOSED CLOSED CLOSED open [each column 1 mark, max 4] B4 [4] (b) (i) power is delivered (by a cylinder) on every stroke M1 (so) smoother power output/torque A1 [2] (ii) improved flow of gases (in and out of cylinder) M1 increases efficiency of engine A1 [2] 12 (a) (i) any agent/substance/waste that is detrimental to health B1 or the environment B1 [2] (ii) 1 man-made: e.g. exhaust gases from cars (anything sensible) B1 2 natural: e.g. volcanic emissions (anything sensible) B1 [2] (b) carbon dioxide absorbed (by plants) with release of oxygen B1 (transpiration) replaces water vapour (in atmosphere) B1 either increasing CO2 levels would cause temperature changes or anything sensible e.g. reference to biodiversity, weather patterns B1 [3] Option T - Telecommunications 13 (a) signal sampled at regular intervals B1 signal voltage converted to a digital number B1 transmitted as a series of groups of pulses B1 pulses could be IR pulses in optic fibre (allow any sensible example) B1 any other relevant physics (e.g. sample at twice max frequency, use parallel to series converter) B1 [5] (b) e.g. can be regenerated to remove noise data can be added to check for/correct errors [anything sensible, 1 each, max 2] B2 [2] 14 (a) (i) loss of energy/power (in the signal) B1 [1] (ii) unwanted (random) signal B1 [1] (b) (i) power/dB = 10 lg(P1/P2) C1 25 = 10 lg (P/(6.0 × 10-19) M1 P = 1.9 × 10-16 W A0 [2] (ii) allowable loss = 10 lg(7.0 × 10-3)/(1.9 × 10-16) C1 = 136 dB C1 length = 136/1.7 = 80 km A1 [3] (c) signal amplifier/re-shaper at intervals along the fibre B1 [1]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – JUNE 2005 9702 6 © University of Cambridge International Examinations 2005 (d) (i) remains at one point above the Earth (1) orbits Earth above the Equator (1) period of orbit is 24 hours (1) rotates from west to east (1) [any two, 1 each] B2 [2] (ii) for satellite, time to travel (2 × 3.6 × 104 km) = 0.24 s B1 for fibre, time to travel 18000 km = 0.06 s → 0.09 s B1 advantage: less built-in delay for conversation B1 [3]