Cambridge A Level Physics 9702 — 2004 Oct/Nov Paper 6 · Variant 1

This document consists of 23 printed pages and 1 blank page. SP (SM/JG) S65136/3 © UCLES 2004 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level PHYSICS 9702/06 Paper 6 October/November 2004 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 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. For Examiner’s Use A F M P T Total

© UCLES 2004 2 9702/06/O/N/04 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 2004 3 9702/06/O/N/04 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 = ±
√(x 0 2 – x 2) 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 [Turn over

4 9702/06/O/N/04 Answer all of the questions in any two Options. 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 Fig. 1.1 lists some distances and some diameters of various objects in the Universe. Fig. 1.1 Complete Fig. 1.1 by naming each distance or diameter. [4] For Examiner’s Use © UCLES 2004 distance or diameter 4.6 light-seconds 16 light-minutes 4.2 light-years 1.2  105 light-years 3  1011 light-years … diameter of Earth’s orbit round the Sun … … …

5 9702/06/O/N/04 2 The Hubble space telescope has provided a means by which very distant galaxies have been discovered. State and explain two reasons why a similar telescope on the Earth’s surface would not enable these discoveries to be made. 1. … … … 2. … … …[4] For Examiner’s Use [Turn over © UCLES 2004

6 9702/06/O/N/04 3 (a) The mean critical density ρ0 of matter in the Universe is related to the Hubble constant H0 and the gravitational constant G by the expression 3H0 2 ρ0 = . 8G (i) Explain the significance of the mean critical density ρ0 for the evolution of the Universe. … … …[2] (ii) Without carrying out any mathematical derivation, explain why the gravitational constant G is a factor in this expression. … … …[2] (b) Fig. 3.1 shows the variation with distance d of the recessional speed v of some galaxies. Note that the graph is a lg-lg plot. Fig. 3.1 For Examiner’s Use © UCLES 2004

7 9702/06/O/N/04 (i) Use Fig. 3.1 to determine an approximate value for 1. the age of the Universe, age = … s [4] 2. the mean critical density of matter in the Universe. critical density = … kg m–3 [2] (ii) Determine the number of nucleons per cubic metre that is equivalent to your answer in (i)2. number = …[2] For Examiner’s Use [Turn over © UCLES 2004

8 9702/06/O/N/04 Option F The Physics of Fluids 4 The densities of liquids may be measured using hydrometers. The hydrometer in Fig. 4.1 consists of a weighted bulb with a thin stem. Fig. 4.1 The hydrometer is floated in the liquid and the density is read from a scale on its stem. The hydrometer in Fig. 4.1 is designed to measure densities between 1.00 g cm–3 and 1.10 g cm–3. (a) On Fig. 4.1, mark with the letter M the position on the scale of the 1.10 g cm–3 graduation. [1] (b) The hydrometer has a mass of 165 g and the stem has a uniform cross-sectional area of 0.750 cm2. Calculate (i) the change in the submerged volume of the hydrometer when it is first placed in a liquid of density 1.00 g cm–3 and then in a liquid of density 1.10 g cm–3, change = … cm3 [4] For Examiner’s Use © UCLES 2004

9 9702/06/O/N/04 (ii) the distance on the stem between the 1.00 g cm–3 and the 1.10 g cm–3 graduations. distance = … cm [1] For Examiner’s Use [Turn over © UCLES 2004

10 9702/06/O/N/04 5 (a) A viscous liquid undergoes laminar flow in a tube. On Fig. 5.1, complete the velocity vectors to represent the flow of liquid along the tube. [2] Fig. 5.1 (b) The volume V of liquid flowing in a streamline manner per unit time along a pipe of length L and radius r is given by the expression r 4 V =  ∆p , 8L where ∆p is the pressure difference between the ends of the pipe and  is the viscosity of the liquid. (i) Suggest why the flow of liquid is measured as a volume flow rate, rather than as a linear speed of the liquid. … …[1] (ii) Determine quantitatively the effect on the volume flow rate of the liquid along the pipe when 1. the pressure difference ∆p is doubled, volume flow rate is … wall of tube For Examiner’s Use © UCLES 2004

11 9702/06/O/N/04 2. the pressure difference ∆p is doubled and the pipe stretches so that its radius r increases by 5.0%. volume flow rate is … [3] For Examiner’s Use [Turn over © UCLES 2004

12 9702/06/O/N/04 6 (a) Describe what is meant by turbulence. … … … …[3] (b) A car is moving through air. The drag force FD on the car is measured at two speeds v. The readings are shown in Fig. 6.1. Fig. 6.1 (i) State and explain whether these data suggest the flow of air round the car is laminar or turbulent. [3] (ii) The drag force on the car at maximum speed is 2.0 103N. Calculate the maximum speed of the car. maximum speed = … m s–1 [2] For Examiner’s Use © UCLES 2004 v / m s–1 30 40 FD/ N 540 970

13 9702/06/O/N/04 Option M Medical Physics 7 (a) Explain briefly the use of ultrasound to obtain diagnostic information about internal body structures. … … … … … … …[5] (b) The variation of the intensity I of a parallel beam of ultrasound with the thickness x (measured in metres) of a muscle is given by the expression I = I0 e–23x , where I0 is the initial intensity. Calculate the fractional intensity transmitted through a muscle of thickness 5.5 cm. = …[2] (c) Having travelled through muscle 5.5 cm thick, the beam is reflected from a muscle/bone boundary. At this boundary, 35% of the incident intensity is reflected. Calculate the fractional intensity that is received back at the transmitter. = …[2] For Examiner’s Use [Turn over © UCLES 2004 I I0 I I0 I I0 I I0

14 9702/06/O/N/04 8 Fig. 8.1 illustrates an eye forming a focussed image of an object O on the retina. Fig. 8.1 It is assumed that all refraction occurs at the surface of the cornea. Whilst viewing the object O, a second object S also appears to be in focus. (a) (i) On Fig. 8.1, draw rays to show the formation of the image of object S. (ii) Hence explain what is meant by depth of focus. … … … [3] (b) Fig. 8.2 shows the same eye viewing the same object O, but in bright sunlight so that the diameter of the iris is reduced. Fig. 8.2 State and explain the effect of this change in the level of illumination on the depth of focus. You may draw on Fig. 8.2 if you wish. … … … …[3] retina iris O retina O S iris For Examiner’s Use © UCLES 2004

15 9702/06/O/N/04 9 A person listens to music using personal headphones. The sound power incident on one eardrum of area 65 mm2 is 0.33 µW. (a) Determine the intensity level I.L. of the sound at the eardrum. I.L. = … dB [4] (b) Suggest the effect on hearing ability of exposure to the intensity level calculated in (a). … …[1] For Examiner’s Use [Turn over © UCLES 2004

16 9702/06/O/N/04 Option P Environmental Physics 10 (a) Briefly describe the process of nuclear fission. … … … …[3] (b) Distinguish between the functions of the moderator and the control rods in a nuclear reactor. moderator: … … … control rods: … … …[4] For Examiner’s Use © UCLES 2004

17 9702/06/O/N/04 11 (a) A water wave may be approximated to a square wave, as illustrated in Fig. 11.1. Fig. 11.1 Such a wave has wavelength λ, amplitude A and speed V. The width of the wave is w. (i) Show that the increase in gravitational potential energy of the water to form one wave crest is
 wA2λρg, where ρ is the density of water and g is the acceleration of free fall. [3] (ii) Hence, by considering the number of wave crests passing a point per unit time, show that the power P of the wave is given by P =
 wA2ρgV. [2] (b) Suggest one environmental problem associated with the harnessing of wave power. … …[1] For Examiner’s Use [Turn over © UCLES 2004 2A w

18 9702/06/O/N/04 12 (a) A room in a house is to be maintained at a temperature of 25 °C when the outside temperature is 5 °C. Fig. 12.1 shows the various components contributing to the rate of loss L of thermal energy from the room. Fig. 12.1 Draw a Sankey diagram for the movement of thermal energy in and out of the room. [3] (b) Two kettles each contain the same mass of water at room temperature. One is a plastic electric kettle with an internal heating element. The other is a steel kettle on a gas ring. Discuss the efficiency of the two kettles as the water is brought to 100 °C. … … … … …[4] For Examiner’s Use © UCLES 2004 walls floor windows ceiling L / W 210 110 420 400

19 9702/06/O/N/04 Option T Telecommunications 13 Fig. 13.1 illustrates part of the electromagnetic spectrum that is used for radio communication. Fig. 13.1 On Fig. 13.1, identify the region of the spectrum that is used for (a) television broadcasts (label this region T), [1] (b) satellite communication (label this region S). [1] For Examiner’s Use [Turn over © UCLES 2004 wavelength in a vacuum 10 km 1 km 0.1 km 10 m 1 m 10 cm 1 cm 1 mm

20 9702/06/O/N/04 14 (a) Explain what is meant by frequency modulation (FM). … … … … …[4] (b) The variation with time t of the signal voltage V transmitted by an aerial is shown in Fig. 14.1. (Fig. 14.1 is on the opposite page.) Use Fig. 14.1 to determine the frequency of (i) the unmodulated carrier wave, frequency = … Hz (ii) the information signal. frequency = … Hz [3] (c) A second system of modulation is amplitude modulation (AM). State one advantage and one disadvantage of FM when compared with AM for nationwide broadcasting. advantage: … … disadvantage: … …[2] For Examiner’s Use © UCLES 2004

21 9702/06/O/N/04 For Examiner’s Use [Turn over © UCLES 2004 Fig. 14.1

© UCLES 2004 For Examiner’s Use 15 The variation with time t of an audio signal is shown in Fig. 15.1. Fig. 15.1 The signal is processed in an analogue-to-digital converter (ADC) before transmission. At the receiver, the signal is processed in a digital-to-analogue converter (DAC). The variation with time t of the received signal, after processing, is shown in Fig. 15.2. Fig. 15.2 22 9702/06/O/N/04

© UCLES 2004 23 9702/06/O/N/04 The ADC and the DAC have the same number of bits. (a) Determine, for this transmission, (i) the sampling frequency, frequency = … Hz (ii) the interval between the voltage levels used in sampling, interval between voltage levels = … V (iii) the number of bits needed to transmit each sample voltage. number of bits = … [4] (b) The waveform of Fig. 15.2 is not a faithful reproduction of that of Fig. 15.1. Suggest and explain minimum values for the sampling frequency and the number of voltage levels of the ADC that are necessary to recover all the main features of the waveform in Fig. 15.1. sampling frequency: … … … number of voltage levels: … … … …[5] For Examiner’s Use

24 9702/06/O/N/04 BLANK PAGE Every reasonable effort has been made to trace all copyright holders where the publishers (i.e. UCLES) are aware that third-party material has been reproduced. The publishers would be pleased to hear from anyone whose rights they have unwittingly infringed. 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 November 2004 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 November 2004 question papers for most IGCSE and GCE Advanced Level syllabuses.

Grade thresholds taken for Syllabus 9702 (Physics) in the November 2004 examination. minimum mark required for grade: maximum mark available A B E Component 6 40 30 27 15 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.

November 2004 GCE A AND AS LEVEL MARK SCHEME MAXIMUM MARK: 40 SYLLABUS/COMPONENT: 9702/06 PHYSICS Paper 6

Page 1 Mark Scheme Syllabus Paper A and AS LEVEL – NOVEMBER 2004 9702 6 © University of Cambridge International Examinations 2005 Option A – Astrophysics and Cosmology 1 diameter of the Sun B1 nearest (neighbour) star/Proxima Centauri B1 diameter of (Milky Way) galaxy B1 extent of (visible) Universe (allow diameter/radius) B1 [4] 2 e.g. Atmospheric absorption/scattering M1 means light is too faint Al Light pollution M1 means light cannot be distinguished against background Al [4] Irregular atmospheric refraction/thermal currents (M1) means small objects blurred/not seen (Al) (any two sensible suggestions {M1 x 2} plus some further detail of each {A1 x 2}) 3 (a)(i) either density such that Universe will not collapse or expand indefinitely B1 greater density than ρ0 means collapse (OR vice versa) B1 or determines whether Universe is ‘open’ or ‘closed’ (B1) greater density than ρ0 means ‘closed’ OR smaller density than ρ0 means ‘open’ (B1) [2] (ii) (if Universe is closed eventually all) kinetic energy of galaxies will be converted to (gravitational) potential energy B1 (gravitational) potential energy involves the gravitational constant G B1 [2] (b) (i)1 (sensible straight line and) one or two points chosen with attempt at antilogs B1 H0 = 100 km s-1 Mpc-1 (allow 80 → 125 km s-1 Mpc-1) A1 1 Mpc = 3.1× 1019 km C1 H0 = 100/(3.1× 1019) = 3.2× 10-18 s-1 Age = 1/H0 = 3.1× 1017 s A1 [4] (i)2 ρ0 = (3× 10-18}2) / (8× π× 6.67× 10-11) C1 = 1.86× 10-26 kg m-3 A1 [2] (ii) number density = (1.86× 10-26) / (1.66× 1027) C1 ≈ 10 A1 [2]

Page 2 Mark Scheme Syllabus Paper A and AS LEVEL – NOVEMBER 2004 9702 6 © University of Cambridge International Examinations 2005 Option F – The Physics of Fluids 4 (a) M shown near base of stem B1 [1] (b) (i) density = mass/volume C1 volume submerged in liquid of density 1.0 g cm-3 = 165 cm3 C1 volume submerged in liquid of density 1.1 g cm-3 = 150 cm3 C1 change in volume = 15 cm3 A1 (ii) distance (= 15/0.75) = 20 cm A1 [5] 5 (a) arrows longer at centre than edges M1 arrows parallel and correct relative lengths A1 [2] (b) (i) no unique value of (linear) speed B1 [1] (ii)1 volume flow rate doubles A1 (ii)2 new radius = 1.05 r new flow rate = 1.054× 2 C1 = 2.4(3) times greater A1 [3] 6 (a) (fluid) flow/movement B1 that is erratic/has eddies B1 i.e. speed varies continuously (in magnitude and direction) with time B1 [3] (b) (i) for turbulent flow, FD/v2 C1 v = 58 m s-1 A1 [2]

Page 3 Mark Scheme Syllabus Paper A and AS LEVEL – NOVEMBER 2004 9702 6 © University of Cambridge International Examinations 2005 Option M – Medical Physics 7 (a) pulse of ultrasound B1 reflected from boundaries B1 received (at surface) and processed B1 time for pulse to return gives depth of boundary B1 reflected intensity gives information on nature of boundary B1 [5] (b) fraction = e-23× 0.055 C1 = 0.28 A1 [2] (c) fraction = 0.28× 0.35× 0.28 C1 = 0.027 A1 [2] (or 0.35e-23× 0.11 = 0.028) 8 (a) (i) rays from S converge to point behind retina B1 (ii) range of image distances B1 such that image is tolerably in focus B1 [3] (b) for the same size of patch on the retina M1 focused image is further from the retina A1 (so) depth of focus is increased B1 [3] 9 (a) intensity = (0.33× 10-6) / (65× 10-6) C1 = 5.1 (5.08) × 10-3 W m-2 C1 I.L. = 10 lg (5.08× 10-3) / (1.0× 10-12) C1 = 97 dB A1 [4] (b) (long-term exposure) could cause deafness OR (short-term exposure) could cause tinnitus B1 [1]

Page 4 Mark Scheme Syllabus Paper A and AS LEVEL – NOVEMBER 2004 9702 6 © University of Cambridge International Examinations 2005 Option P – Environmental Physics 10 (a) massive nucleus/named appropriate nucleus splits B1 into two approximately equal parts/named components B1 with the release of neutrons and energy B1 [3] (b) moderator: slows down (high speed) neutrons M1 so that further fissions are more likely/will take place A1 control rods absorb neutrons M1 to provide control over the rate of fission A1 [4] 11 (a)(i) water moved from (area of) trough to crest to form wave B1 potential energy = mgh M1 = ½ λ Awρ× g× A (must be laid out so that substitutions are obvious) M1 = ½ wA2 λ ρg A0 [3] (ii) there are V/ λ wavecrests passing a point per unit time M1 power = ½ wA2 λ ρg× V/ λ A1 = ½ wA2ρgV A0 [2] (b) e.g hazard to shipping, unsightly, upset to shoaling fish etc. (any sensible suggestion) B1 [1] 12 (a) input shown clearly as 1140 W B1 four outputs labeled correctly M1 arrows having approximately correct ratio of widths A1 [3] (b) electrical heating more efficient at transferring energy to water B1 very little thermal energy escapes because plastic is an insulator B1 gas ring much less efficient because of thermal energy losses to the air B1 thermal energy losses due to conduction as kettle is metal B1 [4]

Page 5 Mark Scheme Syllabus Paper A and AS LEVEL – NOVEMBER 2004 9702 6 © University of Cambridge International Examinations 2005 Option T – Telecommunications 13 (a) box for 1 m – 10 cm labeled T B1 (b) box for 10 cm – 1 cm labeled S B1 [2] 14 (a) frequency of carrier wave varies (in synchrony) with information signal B1 constant amplitude OR carrier frequency >> signal frequency B1 change in frequency measures displacement of information signal B1 rate at which carrier frequency varies gives frequency of information signal B1 [4] (b) (i) period = 0.8 μ s C1 frequency = 1.25 MHz A1 (ii) 125 kHz A1 [3] (c) advantage: e.g. better quality/less interference B1 disadvatange: e.g. more transmitters/more expensive B1 [2] (any sensible suggestions, 1 each) 15 (a) (i) sampled every 0.5 ms C1 frequency = 2.0 kHz A1 (ii) at 1.0 V intervals B1 (iii) 4 bits B1 [4] (b) needs sampling time shorter than smallest peak-trough interval B1 any suggestion of about (0.2 ms or about) 5 kHz (allow 5 kHz → 10 kHz) A1 needs voltage interval less than peak-trough height B1 any suggestion at about 0.3 V (allow 0.1 V → 0.4 V) C1 so either 12/0.3 = 40 OR 11/0.3 = 37 OR 10/0.3 = 34 etc. A1 (ignore binary nature of the ADC and the DAC)