Physics · May / June 2022 · Paper 62 · Question 3
0625
As printed in the paper
The question as text
A student determines the focal length f of a lens. Fig. 3.1 shows the set-up. illuminated object lens y z x bench screen Fig. 3.1
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3(a)(i)[2]
x = 7.5 cm, y = 2.0 cm and z = 5.5 cm
all to nearest millimetre
3(a)(ii)[1]
u = 20 and v = 55
3(a)(iii)[1]
f = 14.6(6666667) (cm)
3(b)[2]
working shown
fA calculation correct
3(c)[2]
any two from:
use darkened room / bright(er) object
move lens slowly (to find sharpest image)
move lens back and forth (to find sharpest image)
ensure that object, lens and screen are vertical
object and (centre of) lens same height (above bench)
perpendicular reading/viewing of the ruler scale
mark the centre of the lens on its holder
3(d)(i)[1]
any integer between 5 and 15 (inclusive)
3(d)(ii)[2]
(a straight line) is a way of taking an average
anomalous results can be seen (and repeated or ignored)
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