Question

The minimum distance between an object and its real image formed by a convex lens is:

• A. 1.5 f
• B. 2 f
• C. 2.5 f
• D. 4 f

Answer 1

The correct option is B 2 f

Four times the focal length, we have the formula,

$\frac{1}{u}+\frac{1}{v}=\frac{1}{f}$ where,

$u,v$ are the object and image distnaces and f is the focal length.

The minimum distnace is achieved when $u=v=2f$

Coincidentally the magnification is -1. (The image is same size as the object,but inverted)