Question

A point object is placed at a distance of 30cm from a convex mirror of focal length 30cm.The image will be formed at

• A. Pole
• B. Infinity
• C. 15cm behind the mirror
• D. 15cm in front of mirror

Answer 1

The correct option is C 15cm behind the mirror

For convex mirror:
Focal length = + 30 cm
u = -30 cm

by using mirror formula

$\frac{1}{f}=\frac{1}{v}+\frac{1}{u}\frac{1}{30}=\frac{1}{v}-\frac{1}{30}\Rightarrow \frac{1}{30}+\frac{1}{30}\frac{1}{v}=\frac{2}{30}v=15cm$

Positive value of v indicates that image will be formed behind the mirror.