, making sure all values are in their standard unit:
The maximum power of the lens system is 64 m1; note that this is positive The image distance, v 2.0 cm 0.02 m. It is a real image and is therefore positive. v 1
1 u 1
f Q 1 u 1 0.02 64Q1 u 50 64Q1 The near point is 7.14 cm from the eye. (ii) Using the formula for power of lenses in contact, making sure all values are in their standard unit:
P P1 P2, where P is the maximum power of the eye, P1 is the power of the cornea and P2 is the power of the variable lens. 64 38 P2
The maximum power of the internal lens is 26 m1. Q
P2 26
‘SECTION A’ EXPERIMENTQUESTIONS
Q1 A student carried out an experiment to verify Snell’s law of refraction by measuring the angle of incidence i and the angle of refraction r for a ray of light entering a substance.The data recorded by the student is shown in the table.
Table 13.8
i / degrees r / degrees
20 13
31 21
42 26
50 30
59 36
70 38
81 42
(i) Describe, with the aid of a diagram, how the student obtained the angle of refraction. (ii) Draw a suitable graph on graph paper and explain how your graph verifies Snell’s law. (iii) Use your graph to calculate the refractive index of the substance.
(iv) State one precaution that should be taken to ensure the accuracy of the result.
Q2 An experiment was carried out to measure the refractive index of a substance. (i) Draw a labelled diagram of the apparatus that could be used in this experiment. (ii) What measurements were taken during the experiment? (iii) How was the refractive index of the substance calculated?
(iv) Give one precaution taken. Give the reason for taking that precaution. (9)
(18) (9) (4)
(12) (12) (10) (6)
Q3 In an experiment to measure the focal length of a converging lens, an approximate value for the focal length was found.The image distance v was then found for a range of values of the object distance u.
