Physics 5054/42 — May/June 2013

Cambridge O-Level · Alternative to Practical · worked solutions for every part, with the mark scheme

questions

marks

minutes

Topics Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials · Experimental Contexts · Observations and Measurements · Planning Experiments and Investigations

Q1Experimental ContextsObservations and MeasurementsAnalysis, Conclusions and EvaluationPlanning Experiments and InvestigationsUse of Techniques, Apparatus and MaterialsFree sample

A student determines the focal length of a lens.

The apparatus is set up as shown in Fig. 1.1.

Fig. 1.1

The illuminated object is fixed at the $0\text{ cm}$ mark on the metre rule.
The perpendicular distance $u$ of the object from the lens is fixed at $15.0\text{ cm}$ .

(a)

On Fig. 1.1, mark $u$ and label it $15.0\text{ cm}$ .

(b)

The image on the screen is not clear and the centre of the image is above the centre of the lens.

Explain how the apparatus is adjusted

(i)

to produce a focussed image on the screen,

(ii)

so that the centre of the image is level with the centre of the lens.

(c)

The image on the screen is in focus.
The student measures the distance from the object to the screen.
Fig. 1.2 shows an enlarged view of part of the screen and the metre rule.

Fig. 1.2

(i)

State the reading on the metre rule at the position of the screen.

reading = ______

(ii)

Use your answer to (c)(i) to calculate the distance $v$ of the image from the lens.

$v$ = ______

(d)

The student repeats the experiment for increasing values of $u$ . The results are recorded in Fig. 1.3.

Fig. 1.3

$u / \text{cm}$	$v / \text{cm}$

20.0	19.8
25.0	16.5
30.0	15.1
35.0	14.2
40.0	13.3

(i)

In the spaces in Fig. 1.3, write your value of $v$ from (c)(ii) and the corresponding value of $u$ .

(ii)

On Fig. 1.4, plot the graph of $v / \text{cm}$ on the $y$ -axis against $u / \text{cm}$ on the $x$ -axis.
Start your graph from $v = 10\text{ cm}$ and $u = 10\text{ cm}$ .
Draw a curved line of best fit.

Fig. 1.4

(e)

Suggest two practical techniques that the student uses to make the readings for $v$ as accurate as possible.

______
______

(f)

When $u = v$ , theory shows that the focal length $f$ of the lens is given by $f = u / 2$ .

Use your graph to determine a value for $f$ .

$f$ = ______

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3 more questions

Q2Analysis, Conclusions and Evaluation · Use of Techniques, Apparatus and Materials6M
Q3Planning Experiments and Investigations · Experimental Contexts · Use of Techniques, Apparatus and Materials · Observations and Measurements · Analysis, Conclusions and Evaluation5M
Q4Experimental Contexts · Use of Techniques, Apparatus and Materials · Observations and Measurements · Analysis, Conclusions and Evaluation6M

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