A real, inverted image of the size of object is to be formed by holding the object at 1 meter from a convex lens, What should be the focal length of the lens? Draw the course of rays.

Explanation

When size of image = size of object, distance of object from convex lens, `u = 2f` where f is focal length of convex lens.
Here, `u =2f = 1 meter`
`:. f=1/2m=0.5 m =50cm`
The course of rays in this case. Distance of object AB from optical centre ( O) of the lens is `|OB|=2f. 100 cm.`