A thin concave lens has a focal length of 20cm. A point object is moved along the principal axis of the lens.
(i) When the object is 40cm in front of the lens, calculate the position and linear magnification of the image.
(ii) The object is now brought to a distance of 25cm from the lens. Calculate the new image distance and magnification.
(iii) Using your results in parts (i) and (ii), sketch qualitatively the variation of magnification with object distance for the range 25cm to infinity and discuss the trend shown by the graph.