Q. A convex mirror forms an image one-fourth the size of the object. If object is at a distance of 0.5 m from the mirror, the focal length of mirror is
A) 0.17 m
B) $-$1.5 m
C) 0.4 m
D) $-$0.4 m
Explanation
(a) $\frac{f}{f - u} = \frac{1}{4} = \frac{f}{f - ( - 0.5)}$
Or $4f = f + 0.5\ or\ 3f = 0.5$
Or $f = \frac{0.5}{3}m = 0.17m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.