Two thin converging lenses are placed on a common axis, so that the centre of one of them coincides with the focus of the other. An object is placed at a distance twice the focal length from the left hand lens. Where will its image be? What is the lateral magnification? The focal of each lens is f.

Answer

A, B

Explanation

The image formed by first lens will be at a distance `2f` with lateral magnification `m_1=-1.` For the second lens this image will behave as a virtual object. Using the lens formula, `1/v-1/u=1/f` we have,
`1/v-1/f=1/f rArr v=f/2`
`m_2=v_2/u_2=((f//2))/f=1/2`
Therefore, final image is formed at a distance `f/2` from the second lens with total lateral
magnification,
`m=m_1xxm_2=(-1)xx(1/2)=-1/2`