Find the equivalent focal length of the system for paraxal rays parallel to axis

Find out equivalent focal length of given lens combination

Find out equivalent focal length of given lens combination

Find the focal length of equivalent system shown in Figure.

Find the focal length of equivalent system shown in Figure.

Find the focal length of equivalent system shown in Figure.

Chromatic aberration is due to (A) Dependence of focal length of a lens on the wave length of light used (B) Dependence of focal length of the lens on the distance of parallel rays from the axis (C) Both A and B (D) Neither 1nor 2

Find focal length of the system shown in figure from left hand side.

Find focal length of the system shown in figure from left hand side.

Let us assume a system that consists of two lenses with focal length f_1 and f_2 respectively. How do you find the focal length of the system experimentally, when? two system are touching each other.