Part (a) This was a fairly popular question among the candidates. Candidates were instructed to measure and record **a**o. However, many responding candidates did not record this value but still calculated the quantity **m = ****. **They scored zero for this column. Intercept was to be determined on the vertical axis, however, majority of the candidates got it on the horizontal axis. Hence, they could not determine the value of **M **for which** U** = 37 cm. The few that got the intercept correctly failed to realize that the value of **m** can be obtained from the value of **m**-1. Few candidates even found it difficult to plot the graph due to the small values of **m**-1.

Part (b). Many could not draw the ray diagram.

The expected answers are that candidates should:

- Measure and record value of
**ao **to at least 1 d.p in cm
- Measure and record
**five** values of **U** to at least 1 d.p in cm

(iii) Measure and record **five** values of to at least1 d.p in cm and in trend

(iv) Correctly evaluate **five** values of **m = **** **to at least 2 d.p

(v) Correctly evaluate **five** values of **m-1 **to at least 3 s.f.

- Show composite table containing
**U**,** a, m and m-1 **

- Plot graph using reasonable scales
- Draw line of best fit
- Determine the slope of the graph and the intercept
- Determine the value of
**U** for which **m-1 = 0**
- State any
**two** of the following precautions

e.g - Avoided parallax error on metre rule/rule.

- Ensured that the arrangement of apparatus are co-axial

- Repeated readings (shown on table)

In part (b), the expected answers are:

**(i) m-1** correctly traced from u – 37cm

**m** correctly evaluated

(ii)

To score

- Object must be beyond 2f.
- Correct image must be between f and 2f on the other side.
- Any two correct rays from the object intersecting to form the image.