O-LevelPhysicsThermal Physics5054/42 · Oct/Nov 2025 · Q210 Marks

A student investigates the absorption of thermal radiation by different coloured surfaces. The student has arranged a thermometer which has a piece of white card attached to its bulb so that the bulb is level with the filament of a lamp. The lamp is switched off. Fig. 2.1 shows the apparatus.

(a)(i)The student: • adjusts the distance d between the white card attached to the thermometer bulb and the lamp until it is approximately 1 cm • records, in Table 2.1, the initial temperature θ_W recorded by the thermometer. The thermometer is shown in Fig. 2.2. Record θ_W in Table 2.1 at time t = 0.[1]
(a)(ii)The student: • switches on the lamp and, at the same time, starts the stop-watch • records, in Table 2.1, the reading on the thermometer every 60s for 5 minutes • switches off the lamp. The student's results are shown in Table 2.1. Table 2.1 time t/s | white card temperature θ_W/°C | black card temperature θ_B/°C ---|---|--- 0 | | 20 | 24 | 28 | 26 | 33 | 28 | 37 | 30 | 41 | 31 | 44 Complete Table 2.1 by completing the time column.[1]
(b)(i)The student • removes the thermometer from the clamp • replaces it with a thermometer with a black card attached to its bulb • repeats the procedure in (a) and records temperatures θ_B. Determine the temperature increase Δθ between t = 0 and t = 300 s for each card.[1]
(b)(ii)Calculate the rate of increase of temperature of each card. Use the equation: rate of temperature increase = Δθ / t Include the unit in your answer.[2]
(b)(iii)Use your answers to (b)(ii) to reach a conclusion which compares the absorption of thermal radiation by the two different cards. State your conclusion.[1]
(b)(iv)A student suggests that the rate of temperature increase is greater at the start of the experiment than at the end. State if the results for the black card support this suggestion. Justify your answer by referring to the results.[2]
(c)State two variables that are controlled in this experiment so that the comparison between the absorbing properties of white and black surfaces is valid.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

[1] 2(a)(i) 21(.0) (°C)
[1] 2(a)(ii) 60, 120, 180, 240, 300
[1] 2(b)(i) 10(.0) °C and 24(.0) °C
[1] 2(b)(ii) 0.033 and 0.08(0)
[1] 2(b)(ii) °C/s
[1] 2(b)(iii) black card is a better absorber (of thermal radiation / heat)
[1] 2(b)(iv) statement matching results (YES)
[1] 2(b)(iv) correct values from the table used (for the same time period)
[1] 2(c) any 2 x 1 mark each: same distance of card from lamp / d
[1] 2(c) any 2 x 1 mark each: same brightness / intensity / current / voltage / power / lamp / heat
[1] 2(c) any 2 x 1 mark each: same area/ thickness / material / size of card
[1] 2(c) any 2 x 1 mark each: same initial / room temperature / allow thermometer or lamp to cool between experiments
[1] 2(c) any 2 x 1 mark each: same (total) time
[1] 2(c) any 2 x 1 mark each: same height of thermometer above the bench