Ray Optics Question 5
Question 5 - 2024 (29 Jan Shift 1)
A convex mirror of radius of curvature $30 \mathrm{~cm}$ forms an image that is half the size of the object. The object distance is :
(1) $-15 \mathrm{~cm}$
(2) $45 \mathrm{~cm}$
(3) $-45 \mathrm{~cm}$
(4) $15 \mathrm{~cm}$
Show Answer
Answer: (1)
Solution:
Given $\mathrm{R}=30 \mathrm{~cm}$
$\mathrm{f}=\mathrm{R} / 2=+15 \mathrm{~cm}$
Magnification $(\mathrm{m})= \pm \frac{1}{2}$
For convex mirror, virtual image is formed for real object.
Therefore, $\mathrm{m}$ is $+\mathrm{ve}$
$\frac{1}{2}=\frac{f}{f-u}$
$u=-15 \mathrm{~cm}$
