Question

A boy is standing 25 m in front of a concave mirror of focal length 20 m. The image will form ________

• A. $100\text{m}$ in front of the mirror
• B. $50\text{m}$ in front of the mirror
• C. $100\text{m}$ behind the mirror
• D. $50\text{m}$ behind the mirror

Answer 1

The correct option is A $100\text{m}$ in front of the mirror

Given,
object distance, $u=-25\text{m}$
focal length, $f=-20\text{m}$
image distance, $v=\frac{uf}{u-f}$
$⟹v=\frac{-25\times -20}{-25-(-20)}$
$⟹v=-100\text{m}$
Hence the iamge is formed 100 m infront of the mirror.