- (a) State the meaning of the term “principal focus” as applied in lenses. (1 mark)
- (b) you are provided with the following apparatus to determine the focal length of a lens:
-a biconvex lens and lens holder.
-a lit candle
-a white screen.
-a metre rule
(i) Draw a diagram to show how you would arrange the above apparatus to determine the focal length of the lens (1 mark)
(ii) Describe the procedure you would follow. (1 mark)
(iii) state two measurements that you would take (2 marks)
(iv) Explain how the measurements in (iii) would be used to determine the focal length. (2 marks)
(c) An object is placed 30 cm infront of a concave lens of focal length 20 cm. Determine the magnification of the image produced. (4 marks)