Physics 5054/41 — October/November 2019

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

questions

marks

minutes

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

Q14MExperimental ContextsObservations and MeasurementsAnalysis, Conclusions and EvaluationFree sample

A student is asked to find the focal length $f$ of a lens. He uses an arrow-shaped slit in a piece of card as an object, as shown in Fig. 1.1.

Fig. 1.1

The object is placed at one end of a metre rule and the lens is fixed a distance $u$ from the object, as shown on Fig. 1.2. The slit is illuminated from behind using a lamp.

A screen is then placed on the metre rule so that a sharp, focussed image of the arrow is formed. The distance $v$ from the lens to the screen is then measured.

Fig. 1.2

(a)

Explain how the student ensures that the image is sharply focussed on the screen.

(b)

Fig. 1.3 is a full-scale diagram showing the positions of the object, centre of lens and screen when the sharp, focussed image is obtained.

Fig. 1.3 (full scale)

(i)

Take measurements from Fig. 1.3 to find $u$ and $v$ .

$u$ = ______ $\text{cm}$
$v$ = ______ $\text{cm}$

(ii)

The focal length $f$ of the lens is given by the equation:

f = \frac{uv}{v + u}

Calculate $f$ , using your measurements in (b)(i).

$f$ = ______ $\text{cm}$

(iii)

Suggest one way the student ensures that his value for $f$ is accurate.

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3 more questions

Q2Observations and Measurements · Experimental Contexts · Use of Techniques, Apparatus and Materials · Analysis, Conclusions and Evaluation13M
Q3Use of Techniques, Apparatus and Materials · Experimental Contexts · Planning Experiments and Investigations · Observations and Measurements · Analysis, Conclusions and Evaluation7M
Q4Experimental Contexts · Use of Techniques, Apparatus and Materials · Observations and Measurements6M

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