(a) Using the above diagram as a guide, carry out the following instructions.
(i) Fix a metre rule on the bench with its graduated side facing up.
(ii) Place the illuminated object at the 0 cm end and the screen at the 100 cm end of the rule such that the distance d between the illuminated object and screen is 100 cm.
(iii) Record the distance d. Also evaluate and record d2 .
(iv) Place and move the converging lens between the illuminated object and the screen until a sharp diminished image of the object is formed on the screen.
(v) Read and record the position l1 of the lens.
(vi) Now move the lens towards the object until another sharp image of the object is formed on the screen.
(vii) Read and record the new position l2 of the lens.
(viii) Evaluate and record L = (l1 – l2), also evaluate L2 and D = d2 - L2.
(ix) Repeat the procedure for four values of d = 85, 75, 65 and 55 cm. Tabulate your readings.
(x) Plot a graph of D on the vertical axis against d on the horizontal axis.
(xi) Determine the slope s, of the graph
(xii) Evaluate k = s
(xiii) State two precautions taken to obtain accurate results.
(b) (i) Explain the statement the focal length of a converging lens is 15 cm.
(ii) Distinguish between a real image and a virtual image. [2 marks]