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GCE JUN 2006 : AS 3A Medical Physics

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2006 assessing Module 3A: Medical Physics ASY31 Physics Assessment Unit AS 3A [ASY31] MONDAY 19 JUNE, AFTERNOON TIME 45 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Answer all five questions. Write your answers in the spaces provided in this question paper. INFORMATION FOR CANDIDATES The total mark for this paper is 45. Quality of written communication will be assessed in question 5(b). Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. Your attention is drawn to the Data and Formulae Sheet which is inside this question paper. You may use an electronic calculator. For Examiner s use only Question Number 1 2 3 4 5 Total Marks ASY3AS6 2318 Marks If you need the values of physical constants to answer any questions in this paper, they may be found on the Data and Formulae Sheet. Examiner Only Marks Remark Answer all ve questions 1 (a) The perception of colour by the human eye is thought to be brought about by the action of different types of cone in the retina. (i) Explain briefly how these types of cone allow colour vision. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) On Fig. 1.1, sketch curves showing how the relative light absorption of each type of cone varies with wavelength. Label the wavelength axis with an appropriate scale. [4] Relative light absorption 0 Fig. 1.1 wavelength /nm wavelength/nm (iii) Also on Fig. 1.1, sketch the overall light absorption curve for the eye. State the wavelength at which the maximum overall sensitivity occurs. Wavelength for maximum sensitivity = _______________nm [2] ASY3AS6 2318 2 [Turn over (b) About one in every hundred males suffers from a form of colourblindness known as protanomaly or red-weakness . Such a person sees any redness in a colour as being much weaker in terms both of depth of colour and brightness. Examiner Only Marks Remark A flower appears pink to a normally-sighted person because it reflects mainly red, but also some blue, light. What colour will the flower appear to be to a person who suffers from protanomaly? _______________________________________________________ [1] ASY3AS6 2318 3 [Turn over 2 (a) Define the terms Examiner Only Marks Remark (i) near point, _____________________________________________________ ___________________________________________________ [1] (ii) far point. _____________________________________________________ ___________________________________________________ [1] (b) A person has a far point distance of 400 cm. (i) Name the defect of vision from which this person suffers. ___________________________________________________ [1] (ii) State the likely cause of this defect. ___________________________________________________ [1] (iii) You are to use the lens equation to determine the power of the lens which would be used to correct the defect. 1. Write down the substitutions you will make for the quantities u and v in this equation. Include relevant signs and units. u = __________________________ v = __________________________ ASY3AS6 2318 4 [2] [Turn over 2. Make these substitutions and calculate the power of the corrective lens. Give the magnitude of the power and state the appropriate unit. Examiner Only Marks Remark Power = ______________________ Unit = _______________________ [2] (iv) The same person has a near point distance of 25.0 cm without spectacles. Calculate the near point distance when he is wearing the spectacles in (b)(iii). Near point distance = _________________ cm ASY3AS6 2318 5 [2] [Turn over 3 (a) The decibel scale is used in the measurement of sound intensity level. Its important feature is that it is a logarithmic scale. Examiner Only Marks Remark Give one reason why it is particularly useful that the decibel scale should be logarithmic. _________________________________________________________ _______________________________________________________ [1] (b) A sound level meter registers 85.0 dB in a certain position when source A operates alone and 87.0 dB when source B operates alone. (i) Calculate the meter reading at this position when both sources are sounding together. (I0 = 1.0 10 12 W m 2) Meter reading = _____________________ dB [4] (ii) Your answer to (b)(i) should not differ greatly from either of the individual readings. Give a reason for this. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] ASY3AS6 2318 6 [Turn over 4 (a) (i) State the normal detectable range of the human ear for a young person. Examiner Only Marks Remark Lower limit: about ______________Hz Upper limit: about ______________Hz [1] (ii) The response of the ear varies with frequency, showing a maximum at a particular frequency. 1. Give an approximate value for this frequency. ________________________________________________ [1] 2. Suggest a physical phenomenon which could lead to this type of behaviour. ________________________________________________ [1] (b) (i) What is meant by frequency discrimination? _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) State qualitatively how the frequency discrimination of the human ear varies across the audible frequency range. _____________________________________________________ ___________________________________________________ [1] ASY3AS6 2318 7 [Turn over In part (b) of this question you should write in continuous prose. You will be assessed on the quality of your written communication. 5 Examiner Only Marks Remark (a) X-rays may be produced by bombarding a metal target with electrons of a suitable energy. Fig. 5.1 is a sketch graph of the way in which the intensity I of the emitted X-rays depends on the wavelength of the radiation when the electrons have been accelerated through a certain potential difference. line spectrum I continuous spectrum short wavelength cut-off 0 0 0 Fig. 5.1 Important features of the spectrum are the continuous spectrum, which terminates in the short wavelength cut-off, and the line spectrum. However, the line spectrum may not always be produced; whether it is or not depends on the tube potential difference. (i) Explain, in terms of energy, why there is a continuous spectrum. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [3] (ii) Explain why the continuous spectrum terminates at a particular wavelength. Show how the cut-off wavelength 0 depends upon the tube potential difference V. _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] ASY3AS6 2318 8 [Turn over (iii) Explain, in terms of energy, why there may be a line spectrum. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (iv) Whether a line spectrum is produced or not depends on the tube potential difference. Explain why. _____________________________________________________ _____________________________________________________ ___________________________________________________ [1] (v) It is often said that about 1% of the electrical energy applied to the accelerating electron beam goes into the production of X-rays. State what happens to most of the remaining 99%. ___________________________________________________ [1] (b) Describe briefly how X-rays are applied in the computed tomography (CT) scanning technique of medical imaging. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] Quality of written communication ASY3AS6 2318 [1] 9 [Turn over THIS IS THE END OF THE QUESTION PAPER ASY3AS6 2318 10 [Turn over S 4/06 4800- 302507(182) GCE Physics (Advanced Subsidiary and Advanced) Data and Formulae Sheet Values of constants speed of light in a vacuum c = 3.00 108 m s 1 permeability of a vacuum 0 = 4 10 7 H m 1 permittivity of a vacuum 0 = 8.85 10 12 F m 1 1 = 8.99 109 F 1 m 4 0 ( ) elementary charge the Planck constant h = 6.63 10 34 J s unified atomic mass unit 1 u = 1.66 10 27 kg mass of electron me = 9.11 10 31 kg 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 on the Earth s surface g = 9.81 m s 2 electron volt ASY3AS6 2318.02 e = 1.60 10 19 C 1 eV = 1.60 10 19 J USEFUL FORMULAE The following equations may be useful in answering some of the questions in the examination: Thermal physics Mechanics Momentum-impulse relation mv mu = Ft for a constant force Average kinetic energy of a molecule 1 m<c2> 2 Power P = Fv Kinetic theory pV = 1 Nm <c2> 3 Conservation of energy 1 mv 2 2 1 mu 2 = Fs 2 for a constant force Simple harmonic motion Displacement x = x0 cos t or x = x0 sin t Velocity v = x 0 2 x 2 Simple pendulum T = 2 l / g Loaded helical spring T = 2 m / k Medical physics Sound intensity level/dB = 10 lg10(I/I0) Sound intensity difference/dB = 10 lg10(I2/I1) Resolving power sin = / D Waves Capacitors Capacitors in parallel 11 1 1 = + + C C1 C 2 C 3 C = C1 + C2 + C3 Time constant = RC Capacitors in series Electromagnetism Magnetic flux density due to current in (i)i long straight (i)i solenoid B= (ii) long straight (i)i conductor B= 0NI l 0I 2 a Alternating currents A.c. generator E = E0 sin t = BAN sin t Particles and photons Two-slit interference = ay/d Diffraction grating d sin = n Stress and Strain Hooke s law F = kx Strain energy E = <F > x (= 1 Fx = 1 kx 2 2 2 if Hooke s law is obeyed) A = N A = A0e t t1 = 0.693/ 2 Photoelectric effect 1 mv2 = max 2 de Broglie equation 1/u + 1/v = 1/ f Radioactive decay Half life Light Lens formula = 3 kT 2 = h /p hf hf0 Particle Physics Nuclear radius 1 r = r0 A3 Electricity Potential divider ASY3AS6 2318.02 Vout = R1Vin/(R1 + R2) ASY31INS

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Additional Info : Gce Physics June 2006 Assessment Unit AS 3A, Module 3A: Medical Physics
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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