2023 · Specimen · 5054/04 | Q2

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Question (2 of 4)10 marks · Practise this topic →

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(a)

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A student investigates the effect of two lenses on the size of a shadow.

He sets up the apparatus as shown in Fig. 2.1.

Fig. 2.1: stand with lamp and lens above graph paper, showing distances x, y and z.

The student uses a small lamp connected to a 3 V power supply.

He attaches the clamp holding the lamp to the highest position on the stand. In this position, the distance z between the lamp and the bench is 56.5 cm.

He places one of the glass lenses in the jaws of a clamp at a distance x = 20 cm below the lamp.

Describe two precautions he takes to ensure the apparatus is set up safely.

Answer guidance

Describe Say what happens, in order. Reasons are not required unless the question also asks why.

[2 marks]

(b)

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Text can be resized with your browser. Refer to the original figures below for diagrams and their layout.

A student investigates how two lenses affect a shadow. Fig. 2.1 shows the apparatus. A small lamp uses a 3 V supply and is clamped at the highest position on the stand. The distance z from lamp to bench is 56.5 cm. One glass lens is clamped x = 20 cm below the lamp. The student switches on the lamp. The lamp light and modelling clay produce a shadow on the graph paper. A second lens is held under the lamp. When it touches the lamp, the shadow diameter D is 2 mm. As this lens moves towards the clamped lens, D decreases; the shadow disappears at x = 9 cm, reappears at x = 10 cm, then increases. At x = 20 cm, D is about six times its value at x = 0. These observations are recorded in Fig. 2.2. Sketch on Fig. 2.3 how D changes with x.

The student switches on the lamp. The lamp light and the modelling clay produce a shadow on the graph paper.

He holds a second lens under the lamp. When this lens is touching the lamp, the diameter D of the shadow of the modelling clay on the graph paper is 2 mm.

The student moves the second lens down towards the clamped lens. He observes the change in D. He records his observations as shown in Fig. 2.2.

Fig. 2.2: recorded observations of how the shadow changes as the second lens moves.

Use the student’s observations to sketch a graph on Fig. 2.3 showing how D changes with increasing x.

Fig. 2.3: blank axes of D against distance of second lens from lamp in cm.

Answer guidance

Draw Accuracy is being marked. Use the figure and be precise about position and labels.

[2 marks]

(c)(i)

The student removes the modelling clay from the clamped lens.

He keeps the lamp at the top of the stand. He can see an image of the lamp on the graph paper on the bench.

He adjusts the position of the clamped lens until the image is as small and bright as possible.

He finds that he cannot position the clamped lens so that the image seen on the graph paper is in focus.

The image is as small and bright as possible when x = 27.6 cm.

Calculate y.

y = ...................................... cm

Answer guidance

Calculate Show your working. The method can earn marks even when the final value is wrong, and a bare answer often cannot.

[2 marks]

(c)(ii)

A student suggests that the focal length f of the lens can be calculated by using the equation

$f$ $= \frac{(x y)}{(x + y)}$

where x and y are determined for a focused image.

Calculate the value of f using this equation, where x = 27.6 cm and y is the value calculated in (c)(i).

Show your working.

f = ...................................... cm

Answer guidance

Show The result is given, so every step of the reasoning is what earns the marks.

[2 marks]

(d)(i)

State why the arrangement of the apparatus shown in Fig. 2.1 cannot be used to accurately determine the focal length f.

Answer guidance

State A short answer. No explanation is needed, and adding one cannot earn extra marks.

[1 mark]

(d)(ii)

Suggest how the arrangement of the apparatus can be changed in order to accurately determine the focal length of the clamped lens.

Answer guidance

Suggest More than one answer may be acceptable, so long as it is consistent with the physics.

[1 mark]

5054/04/SP/23Cambridge O Level Physics 5054 · Specimen 2023 · Paper 4 · Question 2