Coimisi�n na Scr�duithe St�it State Examinations Commission Sc�imeanna Marc�la Fisic Scr�duithe Ardteistim�ireachta, 2004 Gn�thleibh�al Marking Scheme Physics Leaving Certificate Examination, 2004 Ordinary level Coimisi�n na Scr�duithe St�it State Examinations Commission LEAVING CERTIFICATE EXAMINATION PHYSICS � ORDINARY LEVEL MARKING SCHEME 2004 Introduction In considering this marking scheme the following points should be noted. 1. In many instances only key words are given, words that must appear in the correct context in the candidate's answer in order to merit the assigned marks. Marks shown in brackets represent marks awarded for partial answers as indicated in the scheme. Words, expressions or statements separated by a solidus, /, are alternatives which are equally acceptable. Answers that are separated by a double solidus, // , are answers which are mutually exclusive. A partial answer from one side of the // may not be taken in conjunction with a partial answer from the other side. The descriptions, methods and definitions in the scheme are not exhaustive and alternative valid answers are acceptable. The context and the manner in which the question is asked and the number of marks assigned to the answer in the examination paper determine the detail required in any question. Therefore, in any instance, it may vary from year to year. 2. 3. 4. 5. 6. Section A (120 marks) Three questions to be answered. Question 1 40 marks 6+2�3 6 Draw a labelled diagram of the apparatus used in the experiment labelled diagram to show: enclosed / fixed volume of gas / air method of measuring volume e.g. volume scale method of measuring pressure e.g. pressure gauge method of varying pressure / volume NOTE: no labels, deduct 2 Copy this table and fill in the last row by calculating measurement Pressure /kPa Volume /cm3 100 5.0 0.20 111 4.5 0.22 125 4.0 0.25 143 3.5 167 3.0 200 2.5 0.40 any two 2 � 3 1 for each Volume
7�1 250 2.0 0.50 7�1 (3) 1 /cm-3 Volume 0.28/ 0.29 0.33 one mark for filling in each 1/volume including value given 6 inverted values e.g. 1/5, etc. Plot a graph on graph paper of pressure against 1 Volume 4�3 3 3 3 3 label one axis correctly,( name / symbol / unit acceptable) plot three points correctly plot another three points correctly straight line if graph paper is not used, maximum mark 3 � 3 if p versus V is graphed, maximum mark 2 � 3 Explain how your graph verifies Boyle's law 2�3 (straight) line // constant 3 through origin /shows that pressure 1/volume // some correct variation of Boyle's law 3 Give one precaution that the student took in carrying out the experiment after changing pressure wait a short time before taking readings / read the volume of the oil from the bottom of the meniscus / read the volume scale at eye level, safety precaution e.g. do not exceed the pressure limit of the apparatus, etc. any one 3 3 page 1 Q1. Plot a graph on graph paper of pressure against 1 volume Pressure against
0.5 1 volume 0.4 1 /cm - 3 volume 0.3 0.2 0.1 0 0 50 100 150 200 250 Pressure / kPa Pressure /kPa Volume /cm
3 100 5.0 0.20 111 4.5 0.22 125 4.0 0.25 143 3.5 0.28 / 0.29 167 3.0 0.33 200 2.5 0.40 250 2.0 0.50 1 /cm-3 Volume page 1 graph Question 2 40 marks 6+2�3 6 Draw a labelled diagram of the apparatus used labelled diagram to show liquid / water in a calorimeter // block of metal method of heating liquid // method of heating metal stirrer // joulemeter thermometer insulation incorrect experiment, maximum mark 6 + 3 NOTE: no labels, deduct 2 any two 2�3 What measurements of mass did the student take during the experiment? 2�3 mass of substance / liquid / water, mass of metal, mass of calorimeter, mass of calorimeter + liquid/water any two 2 � 3 mass of the metal block (2 � 3) inconsistency between the apparatus and the measurements (3) What temperature measurements did the student take during the experiment? 2 � 3 initial/ minimum temperature of the substance / liquid / water /metal / calorimeter 3 final / maximum temperature of the substance/ liquid / water /metal / calorimeter 3 change in temperature (of the water) (2 � 3) temperature of the substance/ liquid / water /metal / calorimeter (3) Give a formula used to calculate the specific heat capacity of the substance E = mw cw w + mc cc c // E = mw cw w mw cw w / mc cc c Q = / E = / VIt / mc cc c Partial mark e.g. attempts word version of the equation Give one precaution that the student took to get an accurate result lagging, use sensitive thermometer / use a thermometer graduated to 0.1�C, ensure that heating coil is completely immersed in the liquid, stir the liquid, large temperature change, etc. marks above partial answer e.g. repeat / average (3) 10 or 6 or 3 10 (6) (3) (3) 6 or 3 any one 6 the precaution can be implied from the diagram if it has not already been awarded page 2 Question 3 40 marks 6 or 3 6 (3) Name a monochromatic light source sodium (lamp) / laser partial answer e.g. any gas that produces a line spectrum, yellow / red Draw a labelled diagram of the apparatus that you used in the experiment 6+2�3 diffraction grating/ Young's slit 6 monochromatic light source spectrometer // screen scale // metre stick any two 2�3 NOTE: no labels, deduct 2 What readings did you take during the experiment? 6+3 angle on left // distance from grating to screen angle on right // distance between centre and first order grating constant / number of lines per metre any two 6+3 any one 6 What formula did you use to calculate the wavelength of the light? (n) =d/s sin // 3�3 3 3 x D 3 Give one precaution that you took to get an accurate result one spectrometer precaution e.g. ensure the fringe not too wide/not too dim, ensure that the crosshairs are on the centre of the fringe, level the table, focus the telescope (for infinity), measure the angle between the first order images on the left and on the right, adjust the collimator, use the Vernier scale, ensure that the diffraction grating is perpendicular to the (monochromatic) light, use a grating with a large number of lines, ensure D is large, repeat for different orders and take the average, etc. partial answer e.g. repeat the experiment 4 or 2 4
(2) page 3 Question 4 40 marks 6 or 3 6 (3) 4 or 2 4 (2) (6) 6+3 6 3 (3) 4�3 3 3 3 3 Name the instrument used to measure the current ammeter /milliammeter / galvanometer A / multimeter How was the potential difference measured in the experiment? voltmeter V / multimeter / from the voltage ammeter and voltmeter named but in reverse order Name the apparatus Y and give its function in the experiment rheostat / variable resistor / potential divider varies the resistance / potential / voltage / current / power resistor Draw a graph on graph paper of the current against the potential difference label one axis correctly,( name / symbol / unit acceptable) plot three points correctly plot another three points correctly straight line if graph paper is not used, maximum mark 3�3
Current against Potential Difference
3.5 3 2.5 Potential Difference / V 2 1.5 1 0.5 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Current / A Calculate the slope of your graph and hence determine the resistance of the copper sulfate solution 1.67 � 0.2 () or value consistent with graph correct substitution into slope formula // 0.60 slope formula // two points highlighted on the graph
page 4 3�3 3�3 (2 � 3) (3) SECTION B (280 Marks) Five questions to be answered Question 5 any eight parts 56 marks Total the best 8 from 10 parts (a) Calculate the potential energy of the ball 98 (J) substitute into equation (b) Explain the term thermometric property (physical property that) changes (measurably / continually) with (changing) temperature partial answer e.g. valid example 7 or 4 7 (4) 4+3 4 3 (4) (c) Give one application of the Doppler effect 7 or 4 measuring speed / speed gun, (measuring) red shift, ultrasonic scanners, used to study blood flow, used to study heart beat, etc. any correct application 7 partial answer e.g. example of Doppler effect (4) (d) Name two primary colours of light red, blue, green any one (e) Which one of the following is not part of the electromagnetic spectrum? sound waves (f) Name the electrical component represented in the diagram capacitor / condenser partial answer e.g. parallel plate, stores charge, battery (g) Name two safety devices that are used in domestic electric circuits fuse, (trip) switch / miniature circuit breaker / MCB, residual current device / RCD, earthing, etc. (h) Calculate the force on the conductor 7.5 (N) / 750 (T A cm) correctly substituted two quantities into the formula (i) Which one of the following is emitted from a metal surface electrons (j) What is nuclear fission? break up of nucleus / atom partial answer e.g. release of energy / neutrons diagram may merit full marks 7 or 4 any two 7 (4) 7 7 7 or 4 7 (4) 7 or 4 any two 7 any one (4) 7 or 4 7 (4) 7 7 7 or 4 7 (4) page 5 Question 6 56 marks 2 � (2 � 3) 3 3 (2 � 3) (3) rate of change // change in velocity/speed of velocity/speed // per second 3 3 (2 � 3) (3) 4�3 Define (i) velocity, (ii) acceleration (i) velocity: rate of change // distance � time / speed (of) displacement // in particular direction v=
correct unit (ii) acceleration: s t a=
correct unit v -u t Describe an experiment to measure the velocity of a moving object apparatus: trolley timer / photogate // motion sensor procedure: measure distance // connect datalogger to sensor measure time // start program conclusion: v = s t // chose distance versus time graph any four 4�3 accept valid alternatives a labelled diagram may merit marks Sketch a velocity-time graph one labelled axis,( name / symbol / unit acceptable) accelerating from origin to t = 4 s no acceleration from t = 4 s onwards 28 2�4+3 4 4 3 4 14 time Calculate the acceleration of the cheetah during the first 4 seconds a = 7 (m s-2) correct substitution into equation i.e. 28 = 0 + a (4) substitutes one value correctly Calculate the resultant force acting on the cheetah while it is accelerating 1050 (N) / answer consistent with the calculated value for acceleration above correct substitution into formula Name two forces acting on the cheetah while it is running gravitational / gravity / weight friction air resistance / drag (propulsion) force of muscles, etc.
page 6 3�3 3�3 (2 � 3) (3) 6 or 3 6 (3) 2�3 any two 2 �3 Question 7 56 marks 2�3 3 3 2�3 3 3 What is meant by conduction? (transfer) of heat without the movement of matter / atoms // through metals / solids // atoms vibrate // (by vibration) from molecule to molecule Name two other ways of transferring heat convection / example radiation / example Describe an experiment to show how different solids conduct heat at different rates apparatus: a number of different metal rods, heat source procedure: heat all the ends of the rods at the same time, rods same length and same thickness, other valid detail observation/conclusion: e.g. wax melts on (different) rods at different times, (different) rods conduct heat at different rates accept valid alternatives a labelled diagram may merit marks Give two ways in which the U-value of a house can be reduced insulation / fibreglass in attic insulation in cavity wall double glazing carpets 4�3 3 3 3 3 6+2 any two 6 + 2 any one (6) 2�3 3 3 2�3 3 3 (3) 2�3 3 3 (3) 2�3 3 3 (2 � 3) (3) What energy conversion takes place in a solar panel? light / solar to heat Why are the pipes in the solar panel usually made from copper? good conductor / reference to metal partial answer Why are the pipes in the solar panel usually painted black? good // poor absorber (of radiation) // reflector partial answer e.g. black attracts heat Why does the warm water rise to the top of the solar panel? lower density convection / water expands partial answer e.g. it is lighter, reference to water currents page 7 Question 8 56 marks 2�3 3 3 (2 � 3) 2�3 3 3 Explain diffraction spreading out (of a wave) around an obstacle / opening bending of waves around corners labelled diagram or correct example may merit marks Explain interference waves meeting add / change in amplitude / displacement labelled diagram or correct example may merit marks Describe an experiment to demonstrate the interference of sound 6+3+2 apparatus: two sources e.g. two loudspeakers // tuning fork 6 procedure: walk between speakers // rotate (vibrating) tuning fork (near ear) 3 observation/conclusion: observed sound varies in loudness 2 labelled diagram may merit marks accept valid alternatives What is the name given to the points on the string marked (i) X = node / null (point) (ii) Y = antinode correct names mismatched / one correct partial answer e.g. crest/trough How many wavelengths are contained in the distance marked L? two four 6+3 two correct 6 + 3 (6) (3) 6 or 3 6 (3) State two factors on which the natural frequency of a stretched string depends 6 + 3 length / l tension / T thickness / mass per unit length / (linear density) / cross-sectional area / radius / � material any two 6 + 3 any one (6) Calculate the frequency of the note f = 240 - 243 (Hz) correct substitution into both sides of the equation / 340 � 1.4 correct substitution into one side of the equation 3�3 3�3 (2 � 3) (3) page 8 Question 9 56 marks 6+3 two lines What is an electric current? flow of / movement charge / electrons / electricity one line partial answer e.g. unit
Name two other effects of an electric current magnetic / deflects compass chemical partial answer e.g. light / sound Describe an experiment to show the heating effect of an electric current apparatus: source e.g. power supply conductor e.g. bulb, wire procedure: set up the circuit / allow current to flow observation/conclusion: wire gets hot accept valid alternatives a labelled diagram may merit marks 6+3 (6) (3) 6+3 two lines one line 6+3 (6) (3) 4�3 3 3 3 3 State two factors on which the heating effect of an electric current depends 2�3 size of current, (size of) voltage, resistance / length of coil, amount of time any two 2 � 3 Calculate the current that flows through the heater 8.7 (A) / 0.0087 (kA) correct substitution into one side of the equation What is the kilowatt-hour? energy used by a 1 kW (appliance/device) in 1 hour unit used by the ESB partial answer e.g. reference to joule Calculate the cost of using a 2 kW electric heater for 3 hours at 10 cent per kilowatt-hour 60 (cent) / 0.6 (euro) multiplies at least two of the quantities / 2 � 3 / 6 (units) 2�3 2�3 (3) 2�3 3 3 (2 � 3) (3) 2�4 2�4 (4) page 9 Question 10 56 marks 6+3 What is radioactivity? disintegration / decay of nuclei / atoms emission of radiation / energy / / / Name the French physicist who discovered radioactivity in 1896 (Henri) Becquerel / Curie partial answer e.g. named nuclear scientist Name the radiations labelled X, Y and Z in the diagram (i) X = alpha / (ii) Y = gamma / any two lines 6 + 3 any line (6) 6 or 3 6 (3) 6+3+3 three correct 6 + 3 + 3 (iii) Z = beta / (6 + 3) (6) 6 6 6 two correct / all radiations named correctly but mismatched maximum mark any one correct Which one is the most ionising? alpha / / X Name a detector of ionising radiation GM tube / / cloud chamber / ionisation tube / scintillation counter / gold leaf electroscope / solid state detector photographic film, ZnS screen, etc. Outline the principle on which the detectors works ionisation, blackens film, fluorescence partial answer e.g. principle inconsistent with the named detector any one 6 6 or 3 6 (3) (i) Two precautions that should be taken when dealing with radioactive sources 5 or 3 (thick) shielding, long life (containers), never eat / drink / smoke in vicinity, security (against theft), isolating, use protective clothing / gloves / use a tongs when handling, labelling, minimise time spent using radioactive source, keep as far away from source as possible, use warning signs, etc. any two 5 any one (3) (ii) One use of a radioactive source carbon dating, radiotherapy, sterilising medical equipment, killing bacteria in food finding leaks in pipes and seals, checking thickness of materials, smoke alarm tracers in medicine / agriculture, energy source e.g. pacemakers, etc. (iii) One harmful effect of radiation cancer, skin burns, sickness, cataracts, cause sterility, damage to crops, genetic, etc. any one
page 10 3 any one 3 3 3 Question 11 56 marks (a) Draw a diagram to show how a ray of light is transmitted through an optical fibre 7 or 4 incident ray in fibre reflected ray in fibre two correct 7 one correct / no fibre shown (4) (b) How is the escape of light from the sides of an optical fibre prevented? cladding/coating with glass/plastic (of lower/different refractive index), because of total internal reflection partial answer (c) Name a material that is used in the manufacture of optical fibres. glass / plastic / sand / silicon (d) What is the bending of light as it moves from one medium to another called? refraction / refracted
7 or 4 7 (4)
7 7 7 7 (e) What is meant by the refractive index of a material? Sin i Real depth 1 (n =) // // Sin r Sin c Apparent depth // ability to refract / bend light partial answer e.g. one error in equation 7 or 4 7 (4) (f) Define the critical angle. angle in denser medium that gives angle of refraction of 900 4+3 two correct one correct partial answer e.g. depends on the refractive index / where t.i.r. occurs a labelled diagram may merit full marks 7 (4) (4) (g) When will total internal reflection occur? when angle of incidence is greater than critical angle partial answer e.g. when using optical fibres 4+3 two correct one correct 7 (4) (4) (h) Give one use for optical fibres 7 or 4 endoscope, telecommunications, binoculars, correct specific ornament/toy, to supply light to inaccessible places, etc. any one 7 partial answer e.g. ornaments, toys (4) page 11 Question 12 56 marks 2�3 3 3 (2 � 3) 3 3 3�3 3 3 3 (3 � 3) (2 � 3) 3�3+1 3�3 part (a) Define momentum mass (multiplied) by velocity p = mv Give the unit of momentum kg m s-1, N s State the principle of conservation of momentum momentum before equals momentum after (in a closed system / when no external force acts) m1u1 + m2u2 = m1v1 + m2v2 (total) momentum is conserved Calculate the initial velocity of the boat after the child steps out correct substitution into both sides of the equation i.e. 0 = (40)(2) + (50)x each term omitted deduct 3 m1u1 + m2u2 = m1v1 + m2v2 in context 1.6 (m s-1) (2 � 3) (10) part (b) Give one difference between a real image and a virtual image a real image can be obtained on a screen / a virtual image cannot, in a real image the light rays meet / in a virtual image they do not, a real image is always inverted/ a virtual is erect, a real image is in front / a virtual image is behind, etc. Use a ray diagram to show the formation of a real image by a concave mirror one ray reflected correctly second ray reflected correctly How far from the mirror will the image be formed? Equation method Diagram method left hand side of equation substituted correctly // focus shown at 20 cm right hand side of equation substituted correctly // object shown at 30 cm correct rearrangement // image near 60 cm calculation // done on graph paper v = 60 (cm) Give two uses for a concave mirror torch / headlights /searchlight, dentist mirror, cosmetic / shaving mirror, solar furnace, (reflecting) telescopes, etc.
page 12 6 6
2�3 3 3 3�3+1 3 3 3 1 (10)
2�3 any two 2 � 3 part (c) What is electromagnetic induction? emf / voltage / potential difference / current is induced (due to)changing (magnetic) flux / field // moving magnet Name another device that is based on electromagnetic induction dynamo, generator, induction motor, induction cooker, etc. 2�3 3 3 any one 3 3 Name the parts of the transformer labelled A, B and C in the diagram A = primary / input (coil) B = secondary / output (coil) C = (iron) core / former any two any one partial answer e.g. coil in A or B, reference to step-up (transformer) 6+3 6+3 (6) (3) What is the voltage across B? 10 or 6 or 3 690 (V) / three times bigger 10 correct substitution into both sides of the equation / 77 / three times smaller (6) partial answer e.g. correct substitution into one side of the equation (3) part (d) What are X-rays? electromagnetic / stated property e.g. high energy radiation / waves / rays How are electrons emitted from the cathode? thermionic emission / heat partial answer What is the function of the high voltage across the X-ray tube? to accelerate/ pull / attract /give more energy to // to produce electrons // cathode rays / X -rays Name a suitable material for the target in the X-ray tube tungsten, molybdenum Give one use of X-rays to photograph bones/ internal organs, to treat cancer, to detect flaws in materials, to determine the thickness of materials, etc. partial answer e.g. reference to photograph / medicine / industry, etc 2�3 3 3 6 or 3 6 (3) 2�3 3 3 4 4 6 or 3 any one 6 (3) page 13