An object is placed \(4 cm\) away from a concave mirror of focal length \(6 cm\), what is the image position
A. \(12 cm\) behind the mirror
B. \(12 cm\) at the front of the mirror
C. \(3 cm\) behind the mirror
D. \(3 cm\) at the front of the mirror.
Correct Answer: A
Explanation
\(u=4 cm , f=6 cm , v=\) ?
using lens equation;
\(\frac{1}{f}=\frac{1}{u}+\frac{1}{v} ; \frac{1}{6}=\frac{1}{4}+\frac{1}{v}\)
\(\frac{1}{v}=\frac{1}{6}-\frac{1}{4} ; \frac{1}{v}=\frac{2-3}{12}\)
\(\frac{1}{v}=\frac{-1}{12}\)
\(v=-12 cm\) i.e. \(12 cm\) behind the mirror
