Cambridge A Level Physics 9702 — 2003 May/June Paper 6 · Variant 1

Centre Number Candidate Number ; Name CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level PHYSICS 9702/06 Paper 6 Options May/June 2003 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. For Examiner’s Use A F 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. P Stick your personal label here, if T provided. Total This document consists of 16 printed pages. UNIVERSITY of CAMBRIDGE SP (SUF2602/CG) $46468/2 Local Examinations Syndicate © CIE 2003 [Turn over

Data speed of light in free space, permeability of free space, permittivity of free space, elementary charge, the Planck constant, unified atomic mass constant, rest mass of electron, rest mass of proton, molar gas constant, the Avogadro constant, the Boltzmann constant, gravitational constant, acceleration of free fall, c= 3,00 x 108 ms" My = 40 x 10-7 Hm € = 8.85 x 10-1? Fm! e= 1.60x10-19°C h= 6.63 x 10-4 Js u= 1.66 x 10-27 kg m, = 9.11 x 10-31 kg m, = 1.67 x 10-27 kg R= 8.31 JK mol Ng = 6.02 x 1023 mol“! k = 1.38 x 107-73 JK-" G = 6.67 x 107"! Nm? kg? g= 9.81 ms? 9702/6/M/J03

Formulae uniformly accelerated motion, work done on/by a gas, gravitational potential, simple harmonic motion, velocity of particle in s.h.m., resistors in series, resistors in parallel, electric potential, capacitors in series, capacitors in parallel, energy of charged capacitor, alternating current/voltage, hydrostatic pressure, pressure of an ideal gas, radioactive decay, decay constant, critical density of matter in the Universe, equation of continuity, Bernoulli equation (simplified), Stokes’ law, Reynolds’ number, drag force in turbulent flow, s=ut+$at? 2 v? = u?+2as W= pAV o=- am r a=-?x v= vy, cos wt vst V(x3— x?) R=R,+Ao+... R= 1/R, + 1/Ry+... Q 4teyr VC = 1C, + Cy +... C=C, ++... w= tav X= X,sin ot P=pgh p= sect X= X, exp(- At) y= 0:893 4 3H2 Po BnG Av = constant Py + BPVE= Pot BpVE F=Arnv pyr R= OO F= Brpv? 9702/6/M/J03 [Turn over

4 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. Explain briefly what is meant by (a) astar, (b) a galaxy, 2 Outline how the speed, relative to Earth, of a galaxy may be estimated. 9702/6/M/J03 For Examiner's

3 5 (a) A galaxy in the constellation Corona Borealis is estimated to be 430 Mpc away from Earth and receding at a speed of 1.8x10*kms~'. Calculate a value for the Hubble constant Ho. Hg F veeeseeeseseeeeneteeseneseseseeeenenenenes kms7' Mpc [2] (b) Use your answer in (a) to estimate (i) the age, based on the Big Bang model, of the Universe, AGE = oeeeeeesessececserseseeecescsesseseeseessneees s (ii) the speed at which the Moon is receding from the Earth. SPCC = oo. eeeeccscsescseessesseeseesessateatesteas mst [5] (c) Galaxies close to the Milky Way galaxy have been shown to be moving towards the Milky Way galaxy. Suggest whether this observation contradicts the Big Bang model of the Universe. For Examiner's Use 9702/6/M/J03 [Turn over

6 For Examiner's Option F The Physics of Fluids | 4 Alump of pure ice floats on pure water in a beaker, as shown in Fig. 4.1. water. Fig. 4.1 (a) State, qualitatively, the relation between (i) the mass of the ice and the mass of the displaced water, (b) A student marks the level of the water surface in the beaker and then observes the level as the ice melts. State and explain qualitatively the change, if any, in this level during ' the melting. 9702/6/MJO3

7 For Examiner's (a) Asimplified form of the Bernoulli equation may be written as pt ; pv? = constant. State three conditions that must apply to the fluid for this equation to be valid. (b) High-speed trains sometimes pass through stations close to a platform where passengers are standing. In such circumstances, a line may be painted on the platform at some distance from the edge, as illustrated in Fig. 5.1. edge of revom. “(mn oo \ painted line cy aaa Fig. 5.1 Passengers are warned to keep the line between themselves and the platform’s edge. The line is much further from the edge than is required to prevent the passengers being hit by the train. Suggest why this increased distance is necessary. 9702/6/1503 [Turn over

8 6 (a) (i) Explain what is meant by turbulence. (b) The drag force F acting on a car when travelling at speed v in turbulent conditions is given by the expression 1 =5 pPAv?, where p is the density of air and A is the car's frontal area. {i) Identify the symbol Cp. (ii) Show that the power P required to overcome this drag force is given by 1 P= > CppAvs. (iii) For one particular car, Cy is 0.30 and the frontal area A is 2.5 m?. The power P delivered to overcome drag forces is 120 kW. Calculate the maximum speed of the car in air of density 1.2kgm-%. SPCC = oo eeeececeecceecsseeeseteeterseeaeees ms [4] ‘9702/6/M/JO3 For Examiner's

9 Option M Medical Physics 7 (a) Briefly explain the principles of the production of an X-ray beam. (b) State how, in an X-ray tube, (i) the intensity of the X-ray beam may be increased, (c) The intensity of a parallel X-ray beam is reduced to one half of its initial intensity when it passes through bone of thickness 0.40 cm. Calculate the thickness of bone necessary to reduce the beam intensity to one tenth of its initial value. thickness = Examiner's 9702/6/M/J03 [Turn over

10 8 Suggest why, when using a laser as a scalpel, (a) the laser beam is focused using a short focal length convex lens, (b) less bleeding is caused than when using a knife. (b) A person stands in a room where the intensity of the background noise due to a party is 4.5x10-> Wm~. The smallest change in intensity level of sound that can be detected by the person is 3.0 dB. Calculate the change in intensity of sound necessary for the person to hear someone else speak above the background noise. CHANGE = ...eeeescecccseescesseeeeeseeseercaeersenees W mr [3] 9702/6/M/J03 ‘Examiner's

1 For Option P Environmental Physics 10 (a) Explain what is meant by a fossil fuel. (b) By reference to the Earth’s fossil fuels, distinguish between resources and reserves. TOSOUICOS! oo. cessssesessessessescssessensssssessssssvsususevssessnseessensacseasessssesnesesessnsessssssacsessnssnsneensanenseee (b) Explain the role, in a nuclear reactor, of (i) the moderator, (ii) the control rods, (iii) the reactor vessel. 9702/6/M/S03 [Turn over Examiner's

12 12 Ina coal-fired generating station, steam from the boiler enters the turbine at 540°C and leaves at 40°C, as illustrated in Fig. 12.1. exhaust gases steam at 540°C , > turbine generator boiler y steam at 40°C fuel Fig. 12.1 (a) Calculate the maximum efficiency of the turbine. OFFICIONCY = Lo. eeceeeeecceseneteeeseeseeeeseenses [3] (b) The overall efficiency of the generation of electrical energy in the generating station is 30%. (i) Suggest one significant source of loss of energy. 9702/6/M/JO3 For Use

13 ; Examiner's (c) Identify two forms of pollution, other than exhaust gases, associated with coal-fired generating stations. 9702/6/M/J03 {Turn over

14 Option T Telecommunications 13 Fig. 13.1 shows the variation with time t of part of the signal voltage V produced by a microphone. 16 14 12 V/mV 10 0 2 4 6 8 10 12 t/ms Fig. 13.1 The signal voltage is to be digitised using a 4-bit analogue-to-digital converter (ADC), sampling at 2.0 ms intervals. (a) The first sample is taken at time t= 0. Complete Fig. 13.2 to show the signal voltage and the corresponding binary number at the sampling times shown. [4] sampling time /ms signal voltage /mV binary number (e) 2 10 12 1.0 Fig. 13.2 9702/6//JO3 For Examiner's Use

15 (b) The digitised signal voltage is transmitted and then converted back to an analogue signal using a digital-to-analogue converter (DAC). On Fig. 13.3, draw the variation with time tof the received analogue signal V,. [2] 16 14 12 V,/mV 10 t/ms Fig. 13.3 (c) State two changes, giving a reason for each, that can be made so as to improve the quality of the received analogue signal. For Examiner's 9702/6/M/503 [Turn over

16 14 (a) Draw a labelled diagram of a section through a coaxial cable. [2] (b) State three advantages of a coaxial cable compared with a wire pair for the transmission of an electrical signal. 15 A radio signal may be transmitted between a transmitter and a receiving aerial by means of sky waves, ground (surface) waves or space waves. Complete Fig. 15.1 by giving a typical wavelength and the maximum transmission range for each type of wave. [5] type wavelength /m range SKY WAVE J. ensasesstetssersesececesetscnsssses | sesessesenseeeecssceesseeeenseeenees ground (surface) wave SPACE WAVE | siceeesteestestecesentesseecetetee | saeseneeseeeenerensrenteeetseereenees 9702/6/M/J03 For Examiner's