Question

An object is placed in front of a convex mirror at a distance equal to focal length of mirror. The magnification of the object is

• A. zero
• B. $\infty$
• C. $\frac{1}{2}$
• D. 2

Answer 1

Answer: (C)

: For a mirror, $\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$ For convex mirror $f$ is positive For virtual image $v$ is positive $u$ is always negative as per convention $\therefore$ $\frac{1}{v}-\frac{1}{f}=\frac{1}{f}$ or $\frac{1}{v}=\frac{1}{f}+\frac{1}{f}=\frac{2}{f}$ or $v=\frac{f}{2}$ $\therefore$ $\frac{v}{u}=\frac{f}{f\times 2}=\frac{1}{2}$ $\therefore$ Magnification $=\frac{1}{2}$