Q. What is the relative decrease in focal length of a lens for an increase in optical power by $0.1$ D from $2.5$ D? ['D' stands for dioptre]
A) $0.01$
B) $0.04$
C) $0.40$
D) $0.1$
Explanation
[Solution by Dr. Abubacker] $f=\frac1P$, so $\frac{|\Delta f|}f=\frac{\Delta P}P=\frac{0.1}{2.5}=0.04$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.