Cambridge IGCSE Physics 0625 — 2025 Oct/Nov Paper 6 · Variant 2

1 A student investigates the reflection of light by a plane mirror. The student’s ray-trace is shown full-size in Fig. 1.1. M L N 1 2 P R Fig. 1.1 (a) The student: • draws line LN • labels the mid-point of LN with the letter M • draws a line PR parallel to LN and 10.0 cm below it On Fig. 1.1, draw a normal to LN at the point M. Extend the normal downwards until it crosses the line PR. Label the point at which the normal crosses PR with the letter Q. [1] (b) On Fig. 1.1, draw a line 14.0 cm long from point M at an angle θ = 10°, as shown in Fig. 1.2. Label the other end of the line O. [2] M L N θ O Fig. 1.2 (c) The student: • places the reflecting surface of a mirror along the line LN, with its reflecting surface facing the bottom of the page, and with the centre of the mirror at M • positions a light source and slit so that a ray of light passes along the line OM towards M • marks two small crosses X1 and X2, a suitable distance apart on the ray reflected from the mirror • removes the mirror and the illuminated slit. (i) On Fig. 1.1, draw a line joining M to X1 and X2. Continue the line until it crosses the line PR and label the point where it crosses PR with the letter T. [1] (ii) Measure the length a of the line QT in centimetres to the nearest millimetre and the length b of the line MT in centimetres to the nearest millimetre. Record your measurements below and in Table 1.1. a = ......................................................... cm b = ......................................................... cm [1] a (d) Calculate the ratio r = . Record your answer in Table 1.1. b Give your answer to 2 significant figures. Table 1.1 a θ/ ° a / cm b / cm r = b 10 20 4.2 12.8 0.33 30 6.8 13.7 0.50 [2] (e) The student repeats the procedure in (b) and (c) for values of θ = 20° and θ = 30°. The student’s results are recorded in Table 1.1. The student states that r is directly proportional to θ. State if you agree with the student. Use values from Table 1.1 to justify your answer. statement .................................................................................................................................. justification ................................................................................................................................ ................................................................................................................................................... ................................................................................................................................................... [2] (f) Suggest what the student can do to have more confidence in their answer to part (e). ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [1] (g) Suggest one source of inaccuracy in this experiment, even if it is carried out very carefully. ................................................................................................................................................... ............................................................................................................................................. [1] [Total: 11]

Mark scheme: Question Answer Marks 1(a) normal correct (by eye), extended to cross PR and Q labelled 1 1(b) = 10  1 and end of line labelled O 2 MO = 14.0  0.2 cm 1(c)(i) line joining M to the crosses, continued to cross PR 1 1(c)(ii) a = 1.7  0.1 cm 1 b = 10.3  0.1 cm 1(d) r correct 2 answer to 2 significant figures 1(e) statement to match results (expect YES) 2 values from table used to justify statement 1(f) extend the investigation for different values of  1 1(g) reflecting surface of the mirror is at the back/thickness of mirror/small variations in protractor angle have a much larger 1 effect on a and b/ thickness of light ray/difficult to locate centre of light ray/experiment not done in a dark room

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2 A student investigates an electric circuit to find the resistance of an unknown resistor Z. The student sets up the incomplete circuit shown in Fig. 2.1. There is a gap between the points labelled X and Y. Z + – V X Y Fig. 2.1 (a) The student: • closes the switch • records the voltmeter reading V0 • opens the switch. The reading on the voltmeter is shown in Fig. 2.2. Record the voltmeter reading V0. 2 3 1 4 0 5 V Fig. 2.2 V0 = ...................................................... V [1] (b) The student: • connects a 10 Ω resistor between points X and Y • closes the switch • records, in Table 2.1, the reading V on the voltmeter • opens the switch • repeats this procedure for resistors of resistances R = 22 Ω, 39 Ω, 47 Ω and 68 Ω. Table 2.1 resistance R / Ω voltmeter reading V / V current I / A 10 1.35 22 2.20 0.10 39 2.85 0.073 47 0.064 68 3.37 0.050 (i) Use the voltmeter reading in Table 2.1 when the 10 Ω resistor is connected between X and Y to calculate the current I in the circuit. Use the equation: V I = R Record your value of I in Table 2.1 to 2 significant figures. [2] (ii) The voltmeter reading V for the 47 Ω resistor is missing. Calculate V. V = ........................................................... V Add your answer to Table 2.1. [1] (c) Plot a graph of V / V (y-axis) against I / A (x-axis). Start your axes at the origin (0,0). Draw a best-fit straight line. [4] (d) Determine the gradient G of your line. Show all working and indicate on the graph the values you use. G = ......................................................... [2] (e) The gradient of your line is numerically equal to the resistance RZ of the unknown resistor Z. Write down the value of the resistance RZ. Record your answer to the nearest ohm. RZ = ..................................................... Ω [1] [Total: 11]

Mark scheme: 2(a) 4.4(0) (V) 1 2(b)(i) 0.135 /0.14 (A) 2 0.14 (A) 2(b)(ii) 3.0(1) 1 2(c) scales labelled with quantity and unit, correct way around 4 suitable scales (occupying at least ½ the grid) plots correct to  ½ small square and precise plots good best-fit line judgement, thin, continuous line 2(d) indication on the graph as to how gradient found and correct method of calculation of gradient i.e. y / x 2 at least ½ the distance between the extreme plotted points used (I  0.045) 2(e) any integer from 19–25 inclusive 1

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3 A student investigates the cooling of water. The student sets up the apparatus shown in Fig. 3.1. thermometer stand beaker Fig. 3.1 (a) The student records the room temperature θR. θR = .......................21.5 °C The student: • pours 60 cm3 of hot water into the beaker • waits for 30 s • measures, and records in Table 3.1 at time t = 0, the temperature θ of the water • immediately starts a stop-watch and measures the temperature of the water at one-minute intervals for 5 minutes. The reading on the thermometer for time t = 0 is shown in Fig. 3.2. °C 90 80 Fig. 3.2 (i) Record the temperature in Table 3.1 to the nearest 0.5 °C. [1] (ii) Complete the time t column. [1] Table 3.1 time t / ....................... temperature θ / °C 0 80.5 75.5 71.0 67.5 64.0 (b) (i) Suggest why the student waits for 30 s before measuring the initial temperature of the hot water. ........................................................................................................................................... ..................................................................................................................................... [1] (ii) State how the student ensures that the temperature readings are as accurate as possible. ........................................................................................................................................... ..................................................................................................................................... [1] (c) (i) Calculate the decrease in temperature Δθ of the hot water during the first two minutes of cooling. Δθ = .................................................... °C [1] (ii) Calculate the average rate of cooling R1 of the hot water during the first two minutes of cooling. Use the equation: decrease in temperature R1 = time Include the unit in your answer. R1 = ................................. unit = ......................... [2] (iii) Calculate the average rate of cooling R2 of the hot water during the final two minutes of cooling. R2 = ......................................................... [1] (d) Use your answers in (c)(ii) and (c)(iii) to write a conclusion about the way in which hot water in a beaker cools. ................................................................................................................................................... ............................................................................................................................................. [1] (e) The water in the beaker is left to continue cooling. (i) Estimate the temperature of the water θ5 after a further 5 minutes of cooling. θ5 = .................................................... °C [1] (ii) Estimate the temperature of the water θ50 after a further 50 minutes of cooling. θ50 = .....................................................°C [1] [Total: 11]

Mark scheme: 3(a)(i) 87.0 (C) 1 3(a)(ii) min/minute(s) and 1, 2, 3, 4, 5 1 3(b)(i) to get the highest temperature reached/to allow the liquid in the thermometer time to expand/to allow the beaker to warm 1 up/to allow the thermometer to reach the temperature of the hot water/to allow the thermometer (time) to respond/to ensure that the temperature has stopped rising 3(b)(ii) read thermometer perpendicular to the scale/at eye level / hold the stopwatch close to the thermometer/thermometer not 1 touching the sides/base of the beaker/stir the water before taking a reading 3(c)(i) 11.5 C 1 3(c)(ii) R1 = 5.75 / candidate’s (c)(i)  2 2 C / min 3(c)(iii) R2 = 3.5 (C / min) or 0.0583 (C / s) 1 3(d) cooling rate decreases (with temperature/time) 1 3(e)(i) 45–55 (C) inclusive 1 3(e)(ii) room temperature/21.5 C 1

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4 A student sets up a flexible track on the laboratory bench. The student investigates the motion of a metal ball as it rolls from rest down the track. The metal ball rolls down the track, up the other side of the track, and comes momentarily to rest at a height h above the bench before rolling back down again. Plan an experiment to investigate how one variable affects the size of this height h. The apparatus available includes: • flexible track • two clamps, bosses and stands to support the track • selection of metal balls. Fig. 4.1 shows how the flexible track is supported. stand clamp flexible track metal ball path taken by ball h Fig. 4.1 In your plan: • state the one variable you have chosen to investigate • list any additional apparatus needed • explain how to do the experiment • state the key variables to be kept constant • draw a table, with column headings, to show how to display the readings (you are not required to enter any readings in the table) • explain how to use the readings to reach a conclusion. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .................................................................................................................................................... [7]

Mark scheme: 4 variable 1 MP1 valid variable which may affect h stated apparatus 1 MP2 ruler/measuring tape and additional apparatus to measure the independent variable (if not height of release or diameter of ball) method 2 MP3 measure the independent variable and release the ball MP4 measure h and repeat for a new value of independent variable control variable 1 MP5 any significant variable appropriate to the independent variable table 1 MP6 columns with units, for independent variable and dependent variable conclusion 1 MP7 compare readings in the table to see if/how/whether a change in the variable produces a change in h OR plot a (line) graph with axes specified

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