Cambridge IGCSE Sciences - Co-ordinated (Double) 0654 — 2008 May/June Paper 3 · Variant 1

This document consists of 24 printed pages. IB08 06_0654_03/4RP © UCLES 2008 [Turn over *1865284611* For Examiner's Use 1 2 3 4 5 6 7 8 9 Total UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education CO-ORDINATED SCIENCES 0654/03 Paper 3 (Extended) May/June 2008 2 hours 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. You may use a soft pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. A copy of the Periodic Table is printed on page 24. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. www.XtremePapers.com

2 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 1 Fig. 1.1 shows a transverse section through a leaf. The contents of the cells are not shown. xylem A Fig. 1.1 (a) In the space below, make a large, labelled diagram of cell A, to show its structure and contents. [3] (b) State two functions of xylem tissue in a leaf. 1. 2. [2]

3 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (c) A farmer grows spinach in a glasshouse. He decided to use artificial lighting to increase the yield of the crop. He tried out four different wavelengths of light. He measured the volume of carbon dioxide taken up per square metre of leaves per second. He also measured the mass of the spinach leaves that were produced. Table 1.1 shows his results. Table 1.1 wavelength of light / nm units of carbon dioxide taken up per m2 of leaf per second mass of leaves produced / kg per m2 660 6.5 7.8 670 8.3 8.2 680 10.1 8.8 690 9.1 8.3 (i) State two variables that should have been kept constant during this experiment. [2] (ii) Which wavelength of light gave the highest yield? [1] (iii) Explain why the pattern for the units of carbon dioxide taken up is similar to the pattern for the mass of leaves produced. [2] (iv) Explain why plants are able to use some wavelengths of light more than other wavelengths. [2]

4 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 2 Starch, cellulose and proteins are compounds found in plants. (a) (i) State the chemical symbols of the three elements which are combined together in starch. [1] (ii) Plants contain proteins which are compounds containing nitrogen atoms. These atoms have been obtained from gaseous nitrogen in the air by nitrogen fixation. Explain the meaning of the term nitrogen fixation. [2] (b) Ammonium sulphate is a fertiliser which is produced in a reaction between sulphuric acid and ammonia solution. The balanced equation for this reaction is shown below. 2 NH3 + H2SO4 → (NH4)2SO4 In an attempt to produce a solution containing only ammonium sulphate, a student used the following method. 1 50.0 cm3 of a solution containing 2.0 mol / dm3 of ammonia were placed into a glass beaker. 2 50.0 cm3 of a solution containing 2.0 mol / dm3 of sulphuric acid were added to the ammonia solution. (i) Calculate the number of moles of ammonia which the student used. (There are 1000 cm3 in 1 dm3.) Show your working. [2] (ii) Explain whether or not the student had calculated the correct amount of sulphuric acid to use. Show your working. [3]

5 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (iii) The formula of the sulphate ion is SO4 2–. Explain why the formula of ammonium sulphate is (NH4)2SO4. [2]

6 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 3 The circuit in Fig. 3.1 was set up and the current measured by meters M1, M2, M3, M4 and M5. 2 Ω M2 M1 M5 1 Ω M4 1 Ω M3 Y Z Fig. 3.1 (a) (i) The readings on M1 and M2 are shown in Table 3.1. Complete the table for M3, M4 and M5. Table 3.1 M1 = 4A M2 = 1A M3 = M4 = M5 = [1] (ii) Calculate the total resistance of the 2 Ω and 1 Ω resistors in series. [1] (iii) Calculate the total resistance between Y and Z. State the formula that you use and show your working. formula working [3]

7 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (b) The current flows through M1 for one minute. Calculate the charge which has passed. State the formula that you use and show your working. formula working [2] (c) A man walking on a non-conducting floor surface may become positively charged as shown in Fig. 3.2. + + + + – – – – – – – – – – – + + + + + + – – – – Fig. 3.2 Explain in terms of charged particles how he acquired this charge. [3]

8 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 4 A doctor may test a person’s knee-jerk reflex, to check that the nervous system is working properly. When a sharp tap is given just below the kneecap, one of the thigh muscles contracts so that the lower leg moves quickly upwards. Fig. 4.1 shows some of the structures involved in the knee-jerk reflex. tendon kneecap sharp blow here tibia fibula femur stretch receptor thigh muscle neurone neurone spinal nerve spinal cord in section Fig. 4.1 (a) (i) Explain what is meant by a reflex action. [2] (ii) Explain the value of reflex actions to an organism. [2]

9 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (b) (i) On Fig. 4.1, draw a label to one structure that is part of the central nervous system, and label it CNS. [1] (ii) On Fig. 4.1, draw arrows on the two neurones to show the direction of the nerve impulses as they travel from the receptor to the effector. [1] (c) The human skeleton is made of bone and cartilage. Cartilage covers the surfaces of the tibia and femur at the knee joint. (i) Describe the function of cartilage at the knee joint. [2] (ii) State one difference in the properties of bone and cartilage, and explain how this difference helps them to carry out their different functions. [2]

10 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 5 The bodywork of a car is usually made from steel. (a) If part of the bodywork goes very rusty it is usually removed and replaced with plastic filler, before being painted. A car mechanic can use a magnet to find out if parts of the bodywork of a car have been filled with plastic filler. He tests three areas of a car by placing a magnet near the surface as shown in Fig. 5.1. normal bodywork magnet filled hole magnet filled dent magnet paint layer steel plastic filler Fig. 5.1 (i) Complete the table. area effect on a magnet normal bodywork filled hole filled dent weakly attracted [1] (ii) What assumption have you made about the properties of plastic filler? [1] (iii) Would this method work if the bodywork was made of aluminium? Explain your answer. [1] (iv) Suggest why the bodywork of some cars is made from aluminium rather than steel. [1]

11 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (b) After a car has been driven, the tyres are hot. The air in each tyre has a temperature of 45 oC and the pressure of the air in the tyres is 2.5 N / m2. After a while the temperature of the air in the tyres falls to 25 oC. (i) What is the temperature of the air in the tyres in kelvins when the tyres are at 25 oC? K [1] (ii) Calculate the pressure of the air in the tyres at 25 oC, assuming that the volume of the tyre does not change. State the formula that you use and show your working. formula working [3] (iii) Explain in terms of particles why the pressure of the air in the tyres increases when the temperature increases. [2] (c) (i) The car has a mass of 1000 kg. It is travelling at 12 m / s when it collides with a wall. Calculate the kinetic energy of the car before the collision. State the formula that you use and show your working. formula working [2]

12 © UCLES 2008 0654/03/M/J/08 For Examiner's Use (ii) Explain why wearing seat belts can help to lessen the injuries produced in a head- on crash. [2]

13 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use 6 Fig. 6.1 shows some natural processes which occur on and under the Earth's surface. water flowing to sea sea rock A rock B forming in layers and then being pushed into the earth rock C formed from other rocks by heat and pressure molten rock Fig. 6.1 (a) (i) State which rock, A, B or C, was formed when a hot liquid cooled and changed into a solid. [1] (ii) Rock B formed in layers from tiny pieces of solid (sediment) which were washed down to the sea by rivers and compressed. The sediment was produced from rock A whose surface had been damaged by weathering. Describe one way in which the surface of rock A could have been weathered. [2]

14 © UCLES 2008 0654/03/M/J/08 For Examiner's Use (b) A sample of the water flowing into the sea, as shown in Fig. 6.1, was taken to a laboratory for testing. A student observed a drop of water under a microscope. Fig. 6.2 shows a labelled diagram of what he saw. water dispersed solid particles Fig. 6.2 Explain why the water sample looked cloudy and not transparent. You may wish to add some light rays to Fig. 6.2 to help you answer this question. [2] (c) The element bromine is extracted from concentrated solutions of bromine compounds. The reaction between chlorine and sodium bromide solution produces bromine. chlorine + sodium bromide → sodium chloride + bromine (i) Explain why chlorine but not iodine reacts with sodium bromide. [1]

15 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (ii) In the boxes below, draw diagrams of a chlorine atom and a bromide ion, showing only the electrons in the outer shells. chlorine atom bromide ion Cl Br [2] (iii) Describe how the numbers of outer electrons of the particles you have drawn in (ii) change during the reaction of chlorine with sodium bromide. [2] (d) A solution of bromine is used to discover whether a compound is a saturated or unsaturated hydrocarbon. Explain the meanings of the words saturated and unsaturated hydrocarbon. [2]

16 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 7 (a) Fig. 7.1 shows how the action of the enzyme lipase is affected by temperature. 0 10 20 30 40 50 60 rate of reaction temperature / °C Fig. 7.1 (i) State the optimum temperature for this enzyme. [1] (ii) Explain the shape of the curve between 0 ºC and 40 ºC. [3] (iii) Explain the shape of the curve between 45 ºC and 60 ºC. [2]

17 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (b) (i) Describe the sites of production and action of lipase in the human alimentary canal. [2] (ii) Outline the function of lipase. [1] (c) Enzymes are proteins. Name two kinds of proteins that are found in the human body, other than enzymes, and describe their roles. [3]

18 © UCLES 2008 0654/03/M/J/08 For Examiner's Use 8 Heat energy is obtained when hydrocarbon fuels are burned. Natural gas, methane, is an important hydrocarbon fuel. Natural gas is extracted from the Earth's crust. (a) Methane is a fossil fuel formed from the remains of organisms. Describe briefly what has happened to the remains of these organisms that has resulted in the formation of methane. [2] (b) Biogas is an alternative source of methane made from biodegradable materials. Biogas may be obtained from waste materials stored in landfill sites and from controlled reactions in vessels called digesters. Some information about two sources of biogas is shown in Table 8.1. Table 8.1 % of substances in the biogas mixture biogas from a digester biogas from landfill methane 60 – 70 45 – 55 carbon dioxide 30 – 40 30 – 40 nitrogen less than 1 5 – 15 hydrogen sulphide 0.2 0.03 (i) Hydrogen sulphide is made of molecules in which two hydrogen atoms are bonded to one sulphur atom. Complete the bonding diagram below to show • the chemical symbols of the elements in a molecule of hydrogen sulphide, • the arrangement of the outer electrons of each atom. [2]

19 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use (ii) When biogas is burned, any hydrogen sulphide present is oxidised. The symbolic equation below for this reaction is incomplete. State how many molecules of oxygen are required to oxidise two molecules of hydrogen sulphide and explain your answer. 2H2S + …O2 2H2O + 2SO2 number of oxygen molecules explanation [2] (iii) Use the data in Table 8.1 and information in (ii) to suggest and explain one advantage and one disadvantage of burning biogas from a digester rather than from landfill. advantage disadvantage [3]

20 © UCLES 2008 0654/03/M/J/08 For Examiner's Use (c) When liquid nitrogen evaporates, nitrogen molecules, N2, separate and form nitrogen gas. N N N N N N N N liquid nitrogen Explain, in terms of forces of attraction, why molecules of nitrogen rather than individual atoms of nitrogen separate from each other when liquid nitrogen evaporates. [2]

21 © UCLES 2008 0654/03/M/J/08 [Turn over For Examiner's Use 9 (a) Dolphins can communicate underwater by emitting pulses of sound waves which have a frequency of 40 000 Hz. (i) The speed of sound waves in water is 1500 m / s. Calculate the wavelength of these waves. State the formula that you use and show your working. formula working [2] (ii) The speed of sound in air is 330 m / s. Suggest in terms of particles why the speed of sound waves in water is so much greater than the speed of sound waves in air. [2]

22 © UCLES 2008 0654/03/M/J/08 For Examiner's Use (b) The graph in Fig. 9.1 shows the motion of a dolphin travelling through water. 2.5 2.0 1.5 1.0 0.5 0 0 5 10 15 20 25 30 35 time / s speed m / s Fig. 9.1 Calculate the distance covered by the dolphin in the first 25 seconds. Show your working. [2]

23 © UCLES 2008 0654/03/M/J/08 For Examiner's Use (c) A man in a boat sees a dolphin under the water. Draw a ray of light on Fig. 9.2 to show how light travels from the dolphin’s head to the man’s eye. eye air water Fig. 9.2 [3]

24 Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. © UCLES 2008 0654/03/M/J/08 Group 140 Ce Cerium 58 141 Pr Praseodymium 59 144 Nd Neodymium 60 Pm Promethium 61 150 Sm Samarium 62 152 Eu Europium 63 157 Gd Gadolinium 64 159 Tb Terbium 65 162 Dy Dysprosium 66 165 Ho Holmium 67 167 Er Erbium 68 169 Tm Thulium 69 173 Yb Ytterbium 70 175 Lu Lutetium 71 232 Th Thorium 90 Pa Protactinium 91 238 U Uranium 92 Np Neptunium 93 Pu Plutonium 94 Am Americium 95 Cm Curium 96 Bk Berkelium 97 Cf Californium 98 Es Einsteinium 99 Fm Fermium 100 Md Mendelevium 101 No Nobelium 102 Lr Lawrencium 103 1 H Hydrogen 1 7 Li Lithium 3 23 Na Sodium 11 24 Mg Magnesium 12 40 Ca Calcium 20 45 Sc Scandium 21 48 Ti Titanium 22 51 V Vanadium 23 52 Cr Chromium 24 55 Mn Manganese 25 56 Fe Iron 26 59 Co Cobalt 27 59 Ni Nickel 28 64 Cu Copper 29 65 Zn Zinc 30 70 Ga Gallium 31 27 Al Aluminium 13 11 B Boron 5 12 C Carbon 6 14 N Nitrogen 7 16 O Oxygen 8 19 F Fluorine 9 28 Si Silicon 14 31 P Phosphorus 15 32 S Sulphur 16 35.5 Cl Chlorine 17 40 Ar Argon 18 20 Ne Neon 10 4 He Helium 2 73 Ge Germanium 32 75 As Arsenic 33 79 Se Selenium 34 80 Br Bromine 35 84 Kr Krypton 36 39 K Potassium 19 88 Sr Strontium 38 89 Y Yttrium 39 91 Zr Zirconium 40 93 Nb Niobium 41 96 Mo Molybdenum 42 Tc Technetium 43 101 Ru Ruthenium 44 103 Rh Rhodium 45 106 Pd Palladium 46 108 Ag Silver 47 112 Cd Cadmium 48 115 In Indium 49 119 Sn Tin 50 122 Sb Antimony 51 128 Te Tellurium 52 127 I Iodine 53 131 Xe Xenon 54 137 Ba Barium 56 139 La Lanthanum 57 * 178 Hf Hafnium 72 181 Ta Tantalum 73 184 W Tungsten 74 186 Re Rhenium 75 190 Os Osmium 76 192 Ir Iridium 77 195 Pt Platinum 78 197 Au Gold 79 201 Hg Mercury 80 204 Tl Thallium 81 207 Pb Lead 82 209 Bi Bismuth 83 Po Polonium 84 At Astatine 85 Rn Radon 86 Fr Francium 87 227 Ac Actinium 89 9 Be Beryllium 4 I II III IV V VI VII 0 85 Rb Rubidium 37 133 Cs Caesium 55 226 Ra Radium 88 The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). a X b a = relative atomic mass X = atomic symbol b = proton (atomic) number Key *58-71 Lanthanoid series 90-103 Actinoid series DATA SHEET The Periodic Table of the Elements

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education MARK SCHEME for the May/June 2008 question paper 0654 CO-ORDINATED SCIENCES 0654/03 Paper 3 (Extended Theory), maximum raw mark 100 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. 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 discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2008 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses. www.XtremePapers.com

Page 2 Mark Scheme Syllabus Paper IGCSE – May/June 2008 0654 03 © UCLES 2008 1 (a) cell wall and cell membrane in correct positions and labelled ; nucleus and chloroplasts in correct position (in the cytoplasm) and labelled ; vacuole/cytoplasm, labelled ; [3] (b) brings, water/minerals (to leaf) ; support ; [2] (c) (i) temperature ; water ; carbon dioxide concentration ; light intensity ; light duration/day length ; size/age/variety, of plants ; planting distance between plants ; [max 2] (ii) 680 nm ; [1] (iii) carbon dioxide used in photosynthesis ; which produces, glucose/carbohydrates ; converted to other compounds used for building new, cells / tissue ; [max 2] (iv) ref to chlorophyll ; absorbs only some wavelengths ; [2] [Total: 12] 2 (a) (i) C H O ; (all three required) [1] (ii) changing (the element) nitrogen in the air into nitrogen compounds ; extra detail e.g. one way it occurs/reference to inert nitrogen being converted into useful compounds ; [2] (b) (i) obvious use of formula moles = volume × concentration ; (50.0 ÷ 1000) × 2.0 / 0.1 (moles) ; [2] (ii) number of moles of acid used also = 0.1 ; use of equation to show that acid will be in excess ; so solution of ammonium sulphate will not be pure/owtte ; [3] (iii) ammonium ion must be NH4 + ; two positive charges required to balance the double negative of sulphate ; [2] [Total: 10]

Page 3 Mark Scheme Syllabus Paper IGCSE – May/June 2008 0654 03 © UCLES 2008 3 (a) (i) M3 = 1A ; M4 = 3A ; M5 = 4A ; [1] (ii) 3 Ω ; [1] (iii) 1/R = 1/R1 + 1/R2 ; = 1/3 + 1/1 = 4/3 ; R = ¾ Ω ; [3] (b) charge = current × time ; = 4 × 60 = 240 C ; [2] (c) friction ; electron transfer ; from man to floor ; man left with a positive charge ; [max 3] [Total: 10] 4 (a) (i) automatic response ; to a stimulus ; [2] (ii) fast ; avoid danger ; [2] (b) (i) label to spinal cord ; [1] (ii) arrow towards spinal cord on left hand neurone and away on right ; [1] (c) (i) reduce friction ; reduce damage to bone surface ; shock absorber ; [max 2] (ii) bone is stronger/harder than cartilage or cartilage more flexible than bone ; cartilage effective as shock absorber/bone provides support ; cartilage has a smoother surface than bone ; so reduces friction at joints ; [2] [Total: 10]

Page 4 Mark Scheme Syllabus Paper IGCSE – May/June 2008 0654 03 © UCLES 2008 5 (a) (i) (normal bodywork) strongly attracted ; (filled hole) not attracted ; [1] (ii) (plastic filler) is not magnetic ; [1] (iii) no – aluminium is not magnetic ; [1] (iv) aluminium does not corrode/corrodes less than steel ; [1] (b) (i) 298 K ; [1] (ii) P1/T1 = P2/T2 ; 2.5/318 = P2/298 ; P2 = 2.3 N/m2 ; [3] (iii) kinetic energy of particles increases/move faster ; more frequent collisions with tyre walls ; [max 2] (c) (i) kinetic energy = ½ mv2 ; = ½ ×1000 × 12 × 12 = 72 000 J ; [2] (ii) seat belt, reduces/removes, kinetic energy from passenger ; stops collision with windscreen ; [2] [Total: 14]

Page 5 Mark Scheme Syllabus Paper IGCSE – May/June 2008 0654 03 © UCLES 2008 6 (a) (i) A ; [1] (ii) (biological) roots ; abrade rock surface ; animals ; abrade rock surface ; (physical) description of freeze/thaw ; reference to ice expansion ; description of thermal variation ; expansion/contraction cause surface damage ; particles carried by wind ; abrade rock surface ; (chemical) acidic rain ; reacts with rock ; [max. 2] (b) for transparency light rays must pass through undeviated/owtte ; light rays scattered when passing through colloid/shown on diagram ; [2] (c) (i) chlorine more reactive than bromine/free halogen must be more reactive than halide in compound/iodine is less reactive than bromine ; [1] (ii) 7 electrons on chlorine ; 8 electrons on bromide ; [2] (iii) chlorine becomes 2,8,8/gains an electron/gains a full shell ; bromide loses an electron/now has 7 electrons in outer shell ; [2] (saying one electron transfers from bromide to chlorine gains both marks) (d) saturated – only single bonds (between C atoms)/contains as much H as possible ; unsaturated – contains double bond(s)/more H could be added ; [2] [Total: 12]

Page 6 Mark Scheme Syllabus Paper IGCSE – May/June 2008 0654 03 © UCLES 2008 7 (a) (i) 44 °C ; [1] (ii) particles have more kinetic energy ; more frequent collisions ; more energetic collisions ; between substrate and, enzyme/active site ; [max 3] (iii) enzyme needed to catalyse reaction ; enzyme, (molecules) lose shape/denatured (at high temperatures) ; substrate, cannot bind with/does not fit, active site ; [max 2] (b) (i) produced in pancreas ; acts in, small intestine/duodenum/ileum ; [2] (ii) converts, fats/lipids, to fatty acids and glycerol ; [1] (c) haemoglobin ; carries oxygen ; antibodies ; destroy pathogens ; keratin ; forms hair/nails/outer layers of skin ; insulin/glucagon ; control blood sugar level ; collagen ; provides, strength/elasticity, in skin/bone/cartilage ; any two roles, max two marks from one role and one mark from another [max 3] [Total: 12]

Page 7 Mark Scheme Syllabus Paper IGCSE – May/June 2008 0654 03 © UCLES 2008 8 (a) over millions of years ; remains have been heated ; subjected to pressure ; decomposed by bacteria ; in absence of oxygen ; [max. 2] (b) (i) correct bonding electrons ; lone pairs on sulphur ; [2] (ii) 3 ; must be the same number of each type of atom on both sides ; [2] (iii) advantage greater % of methane ; so more efficient fuel/more heat from a unit mass ; disadvantage greater amount of hydrogen sulphide ; so more atmospheric pollution/reference to consequences of SO2 ; [3] (c) attractive forces within molecules are very strong/chemical bonds holding atoms together are very strong ; forces between nitrogen molecules are very weak/much less energy needed for molecules to separate than to break ; [2] [Total: 11] 9 (a) (i) velocity = frequency × wavelength ; wavelength = 1500 / 40 000 = 0.0375 m ; [2] (ii) sound travels through particle vibration ; vibrations travel better when particles are closer together ; [2] (b) area under graph/working ; 3.75 + 15 + 5 + 5 ; = 23.75 m ; [2] (c) straight lines with arrows ; bending at surface ; entering eye ; [3] [Total: 9]