Question

If f is the focal length of the lens, then the power of a lens is equal to

• A. $\frac{100}{f\left(cm\right)}$
• B. $\frac{10}{f\left(cm\right)}$
• C. $\frac{100}{f\left(m\right)}$
• D. $\frac{1}{100f\left(cm\right)}$

Answer 1

The correct option is A $\frac{100}{f\left(cm\right)}$

Power of lens, $P=\frac{100}{f\left(cm\right)}$.
When power increases, the focal length decreases. Dioptre is the unit of measure for the refractive power of a lens.