Question

Three convex lenses are available having focal lengths of $4cm,40cm$ and $4m$ respectively. Which one could be used as magnifying glass?

• A. $4cm$
• B. $40cm$
• C. $4m$
• D. All

Answer 1

The correct option is A $4cm$

Power of lens, $p=\frac{1}{f\left(m\right)}$

power of a lens is inversely proportional to its focal length, less focal length more converging power of lens and hence more magnification.

Hence, convex lens of focal length $4$cm can be used as magnifying glass.

Answer-(A)