Question

An object is placed at the following distance from a convex lens of focal length 15 cm:

(a) 35 cm
(b) 30 cm
(c) 20 cm
(d) 10 cm
Which position of the object will produce:
(i) a magnified real image?
(ii) a magnified virtual image?
(iii) a diminished real image?
(iv) an image of same size as the object?

Answer 1

(a) The object should be placed at 20 cm because a convex mirror forms a real, magnified image when an object is placed between f and 2f.
(b) The object should be placed at 10 cm because a convex mirror forms a virtual, magnified image when an object is placed placed between f (focus) and the optic centre.
(c) The object should be placed at 35 cm because a convex mirror forms a real, diminished image when an object is placed beyond 2f.
(d) The object should be placed at 30 cm because a convex mirror forms a real image of the same size when an object is placed at 2f.