(a) (i) What is meant by focal length of a lens?
(ii)Calculate the power of a concave lens focal length 20cm.
(b) An object of height 7.5 cm is placed at a distance of 15cm from a convex lens of focal length 20cm. by scale drawing determine the
(i) height of the image
(ii) image distance
(c ) Describe an experiment to determine the focal length of a convex lens using an illuminated object and a plane mirror.
(d) What is the main difference between the operation of a lens camera and that of a human eye?