Question

An image of small size can be obtained on a screen placed at 2.0 m from object. It can be done by using.

• A. concave mirror of focal length 0.5 m
• B. concave mirror of focal length greater than 0.5 m
• C. concave mirror of focal length less than 0.5 m
• D. concave lens of focal length less than 0.5 m

Answer 1

The correct option is C concave mirror of focal length less than 0.5 m

using concave mirror $:$ let object distance is $d$

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

$\frac{-1}{\left(d-2\right)}-\frac{-1}{d}=\frac{1}{f}$

$\Rightarrow \frac{-d-d+2}{d\left(d-2\right)}=\frac{1}{f}$

$\Rightarrow f=\frac{d\left(d-2\right)}{2}$

Hence,

option $\left(C\right)$ is correct answer.