Question

An object is kept at $15cm$ from a convex mirror of focal length $25cm$. Calculate the image distance.

• A. $9.37cm$ behind the mirror
• B. $9.3cm$ in front of the mirror
• C. Insufficient data
• D. $15cm$ behind the mirror

Answer 1

The correct option is A $9.37cm$ behind the mirror

Given: An object is kept at 15cm from a convex mirror of focal length 25cm.

To find the image distance

Solution:

according to the question,

object distance , $u=-15cm$, focal length, $f=25cm$

By the mirror formula

$\frac{1}{f}=\frac{1}{v}+\frac{1}{u}$

$\frac{1}{25}=\frac{1}{v}-\frac{1}{15}⟹\frac{1}{v}=\frac{1}{25}+\frac{1}{15}⟹\frac{1}{v}=\frac{3+5}{75}⟹v=\frac{75}{8}⟹v=9.37cm$

Hence the image distance is 9.37cm behind the mirror.