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GCE JUN 2008 : AS 3A Medical Physics

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education 2008 Physics assessing Module 3A: Medical Physics ASY31 Assessment Unit AS 3A [ASY31] THURSDAY 19 JUNE, MORNING 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(c). 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 Formula 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 4662 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 parts of the eye do certain things. Complete Table 1.1 below. Table 1.1 Part of the eye What it does Carries information to brain Cornea Detects the image [3] (b) (i) Describe how a focused image is formed for objects at different distances from the eye. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] (ii) Describe how the eye adapts over a period of time to an increase in the brightness of light. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] 4662 2 [Turn over 2 A person has normal distant vision, but a near point of 0.80 m. Examiner Only Marks Remark (a) (i) What name is given to this type of defective vision? ____________________________________________________ [1] (ii) Suggest two possible causes of this condition. ______________________________________________________ ____________________________________________________ [2] (iii) What type of lens is used to correct this condition? ____________________________________________________ [1] (b) (i) Calculate the power of the spectacle lens required to correct the near point of the person in (a) to enable him to see clearly objects 0.25 m from his eyes. Power = _________ Unit _________ [3] (ii) What will his far point be when wearing these spectacles? Far point distance = _________ m 4662 [2] 3 [Turn over 3 (a) (i) State two reasons for using the decibel scale to measure sound intensity levels. Examiner Only Marks Remark 1. ____________________________________________________ 2. __________________________________________________ [2] (ii) Above what intensity level is noise generally accepted to be harmful? ____________________________________________________ [1] (b) An office worker hears the noise of roadworks coming through an open window. The sound intensity at her ear is 5.6 10 3 W m 2. (i) What is the meaning of the term noise in this context? ______________________________________________________ ____________________________________________________ [1] (ii) Calculate the intensity level of the noise. (I0 = 1.0 10 12 W m 2) Intensity level = ___________ dB [2] (iii) She closes the window, which reduces the sound intensity level by 15 dB. Calculate the sound intensity at her ear when the window is closed. Intensity = _____________ W m 2 4662 [3] 4 [Turn over 4 (a) (i) State the range of frequencies detectable by a typical human ear. Examiner Only Marks Remark ____________________________________________________ [1] (ii) What is meant by the threshold of hearing? ______________________________________________________ ____________________________________________________ [1] (b) (i) On Fig. 4.1 sketch a graph to show how the minimum detectable intensity varies with frequency for a typical ear. On your graph mark the frequency at which the ear is most sensitive. Use shading to indicate where sounds are detectable. 102 01 Imin/Wm 2 10 2 10 4 10 6 10 8 10 10 10 12 10 14 10 16 1 10 102 103 104 Fig. 4.1 f/Hz 105 [4] (ii) Briefly describe how the ability to discriminate between frequencies changes across the detectable frequency range. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] 4662 5 [Turn over 5 In part (c) of this question you should answer in continuous prose. You will be assessed on the quality of your written communication. Examiner Only Marks Remark (a) (i) Describe the basic principle of operation of an ultrasonic generator when used to produce ultrasound. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] (ii) There is a distinct difference between the information that can be obtained from an ultrasonic A-scan and an ultrasonic B-scan. State this difference. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] (b) (i) Describe briefly how X-rays are produced. ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] (ii) In what way does a conventional X-ray image differ from an image produced by X-ray tomography? ______________________________________________________ ____________________________________________________ [1] 4662 6 [Turn over (c) Both ultrasound B-scans and computerised tomography are widely used in medical diagnosis. Briefly compare the two types of imaging. In your answer you should refer to Examiner Only Marks Remark (i) similarities and differences in the basic techniques used, (ii) advantages and disadvantages of each method. ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ______________________________________________________ ____________________________________________________ [4] Quality of written communication [1] THIS IS THE END OF THE QUESTION PAPER 4662 7 [Turn over S 11/07 531-012-1 0 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 e = 1.60 10 19 C 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 1 eV = 1.60 10 19 J ASY31INS 4662.02 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= = ay/d Diffraction grating 0I 2 a A.c. generator E = E0 sin t = BAN sin t 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) Electricity Vout = R1Vin/(R1 + R2) 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 4662.02 l Alternating currents d sin = n Potential divider 0NI Particles and photons Two-slit interference Lens formula = 3 kT 2 = h /p Particle Physics Nuclear radius 1 r = r0 A3 hf hf0

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Additional Info : Gce Physics June 2008 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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