Cambridge A Level Physics 9702 — 2016 May/June Paper 5 · Variant 1

This document consists of 8 printed pages. DC (LEG/SG) 109582/2 © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 3 4 0 0 6 6 0 3 5 6 * PHYSICS 9702/51 Paper 5 Planning, Analysis and Evaluation May/June 2016 1 hour 15 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. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. 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.

2 9702/51/M/J/16 © UCLES 2016 1 A student is investigating the characteristics of different light-emitting diodes (LEDs). Fig. 1.1 shows examples of LEDs and the circuit symbol for an LED. blue red circuit symbol: Fig 1.1 Each LED needs a minimum potential difference V across it to emit light. The student is investigating the relationship between V and the wavelength λ of the light emitted by the LED for several different LEDs. It is suggested that the relationship is V = kλn where k and n are constants. Design a laboratory experiment to test the relationship between V and λ. Explain how your results could be used to determine values for k and n. You should draw a diagram, on page 3, showing the arrangement of your equipment. In your account you should pay particular attention to • the procedure to be followed, • the measurements to be taken, • the control of variables, • the analysis of the data, • any safety precautions to be taken. [15]

3 9702/51/M/J/16 © UCLES 2016 [Turn over Diagram … … … … … … … … … … … … … … …

4 9702/51/M/J/16 © UCLES 2016 … … … … … … … … … … … … … … … … … … … … … … … … … … … [Total: 15]

5 9702/51/M/J/16 © UCLES 2016 [Turn over 2 A student is investigating how the extension of a loaded wire depends on the diameter of the wire. The apparatus is set up as shown in Fig. 2.1. wire load F Fig. 2.1 A load F is applied to the wire and the extension e is measured. The experiment is repeated for wires of the same material and same initial length L but different diameter d. It is suggested that e and d are related by the equation e = 4LF πEd 2 where E is a constant. (a) A graph is plotted of e on the y-axis against 1 d 2 on the x-axis. Determine an expression for the gradient. gradient = …[1]

6 9702/51/M/J/16 © UCLES 2016 (b) Values of d and e are given in Fig. 2.2. d / 10–3 m e / 10–3 m 0.28 ± 0.02 11.3 0.32 ± 0.02 8.6 0.38 ± 0.02 6.0 0.46 ± 0.02 4.1 0.56 ± 0.02 2.7 0.72 ± 0.02 1.7 Fig. 2.2 Calculate and record values of 1 d 2 / 106 m–2 in Fig. 2.2. Include the absolute uncertainties in 1 d 2. [3] (c) (i) Plot a graph of e / 10–3 m against 1 d 2 / 106 m–2. Include error bars for 1 d 2. [2] (ii) Draw the straight line of best fit and a worst acceptable straight line on your graph. Both lines should be clearly labelled. [2] (iii) Determine the gradient of the line of best fit. Include the absolute uncertainty in your answer. gradient = …[2]

7 9702/51/M/J/16 © UCLES 2016 [Turn over 1 1.0 3.0 5.0 7.0 9.0 11.0 13.0 15.0 2 3 4 5 6 7 8 9 10 11 12 1 d 2 / 106 m–2 e / 10–3 m

8 9702/51/M/J/16 © UCLES 2016 (d) (i) Using your answers to (a) and (c)(iii), determine the value of E. Include an appropriate unit. Data: L = 2.50 ± 0.01 m and F = 19.0 ± 0.5 N. E = …[2] (ii) Determine the percentage uncertainty in E. percentage uncertainty in E = … % [1] (e) The experiment is repeated with a thinner wire of diameter 0.23 ± 0.02 mm. The wire is of the same material and initial length. Determine the extension e of the wire when the same load is added to it. Include the absolute uncertainty in your answer. e = …m [2] [Total: 15] To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series.

® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 4 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level PHYSICS 9702/51 Paper 5 Planning, Analysis and Evaluation May/June 2016 MARK SCHEME Maximum Mark: 30 Published 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, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2016 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9702 51 © Cambridge International Examinations 2016 Question 1 Planning (15 marks) Defining the problem (2 marks) P λ is the independent variable, or vary λ. [1] P V is the dependent variable, or measure V. [1] Methods of data collection (4 marks) M Circuit diagram showing d.c. power supply in series with diode (correct symbol needed) and method to measure potential difference across diode. Circuit must be correct. [1] M Instrument to change p.d. across LED e.g. variable power supply/potential divider/variable resistor. [1] M Record wavelength of light of LED from data sheet or use Young’s slits/diffraction grating. [1] M (Slowly) increase potential difference across LED until LED (just) emits light (or reverse procedure). [1] Method of analysis (3 marks) A Plot a graph of lg V against lg λ (allow natural logs). Allow lg λ against lg V. [1] A n = gradient [1] A k = 10y-intercept [1] Additional detail (6 marks) Relevant points might include: [6] 1 Use of a protective resistor (can be shown on the diagram). 2 Polarity of LED correct in circuit diagram. 3 Instrument to determine when LED just lights e.g. light meter/detector, LDR. 4 Method to use light detector/LDR to determine point at which LED emits light. 5 Expression that gives λ (symbols need to defined) from experimental determination of wavelength of light, e.g. Young’s slits/diffraction grating. 6 Perform experiment in a dark room/LED in tube. 7 Relationship is valid if graph is a straight line. 8 λ = + lg lg lg V n k 9 Repeat V and average for the same λ or LED. Do not allow vague computer methods.

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9702 51 © Cambridge International Examinations 2016 Question 2 Analysis, conclusions and evaluation (15 marks) Mark Expected Answer Additional Guidance (a) A1 π 4LF E (b) T1 2 1 d / 106 m–2 T2 13 or 12.8 9.8 or 9.77 6.9 or 6.93 4.7 or 4.73 3.2 or 3.19 1.9 or 1.93 All values to 2 s.f. or 3 s.f. Allow a mixture of significant figures. Must be values in table. U1 From ± 2 to ± 0.1 Allow more than one significant figure. (c) (i) G1 Six points plotted correctly Must be within half a small square. Do not allow “blobs”. ECF allowed from table. U2 Error bars in 2 1 d plotted correctly All error bars to be plotted. Must be accurate to less than half a small square. (ii) G2 Line of best fit If points are plotted correctly then lower end of line should pass between (3.2, 3.0) and (3.6, 3.0) and upper end of line should pass between (11.2, 10.0) and (11.6, 10.0). G3 Worst acceptable straight line. Steepest or shallowest possible line that passes through all the error bars. Line should be clearly labelled or dashed. Examiner judgement on worst acceptable line. Lines must cross. Mark scored only if error bars are plotted. (iii) C1 Gradient of line of best fit The triangle used should be at least half the length of the drawn line. Check the read-offs. Work to half a small square. Do not penalise POT. (Should be about 9 × 10–10.) U3 Absolute uncertainty in gradient Method of determining absolute uncertainty Difference in worst gradient and gradient. (d) (i) C2 = π× 4 60.479 gradient gradient LF Do not penalise POT. (Should be about 7 × 1010.) C3 N m–2 or Pa Allow in base units: kg m–1 s–2. (ii) U4 Percentage uncertainty in E Must be larger than 3%.

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9702 51 © Cambridge International Examinations 2016 Mark Expected Answer Additional Guidance (e) C4 e in the range 15.5 × 10–3 to 18.0 × 10–3 and given to 2 or 3 s.f. Allow mm. U5 Absolute uncertainty in e Note = 2 gradient e d is possible. Uncertainties in Question 2 (c) (iii) Gradient [U3] uncertainty = gradient of line of best fit – gradient of worst acceptable line uncertainty = ½ (steepest worst line gradient – shallowest worst line gradient) (d) (ii) [U4]     ∆ ∆ = + + × = × +         gradient 0.01 0.5 gradient percentage uncertainty 100 100 3.03% gradient 2.50 19.0 gradient × × × × = = = π× π× 4 max max 4 2.51 1 9.5 62.319 max min gradient min gradient min gradient L F E 4 min min 4 2.49 18.5 58.652 min max gradient max gradient max gradient L F E × × × × = = = π× π× (e) [U5]     = + + × × + = +         0.5 0.01 0.02 percentage uncertainty 2 100 % 20.4% % 19.0 2.50 0.23 E E   ∆   = + × ×         gradient 0.02 percentage uncertainty 2 100 gradient 0.23 = 2 min max gradient max e d × × = π× × max max 2 min min 4 max L F e E d = 2 max min gradient mine d × × = π× × min min 2 max max 4 min L F e E d