Question

An object of length $6cm$ is placed on the principle axis of a concave mirror of focal length $f$ at a distance of $4f$. The length of the image will be

• A. -$2cm$
• B. $12cm$
• C. $4cm$
• D. $1.2cm$

Answer 1

Answer: (A)

-$2cm$

Given that,

The object distance $u=-6cm$

Now, magnification is

$m=\frac{I}{O}$

$m=\frac{f}{f-u}$

$\frac{I}{6}=\frac{-f}{-f-(-4f)}$

$I=-2cm$

Hence, the length of image is -$2cm$