Question

A plane mirror of length $90\text{cm}$ is mounted on the wall in a barber shop. What is the maximum height a man can have to see his own image completely in the mirror ?

• A. $90\text{cm}$
• B. $45\text{cm}$
• C. $180\text{cm}$
• D. $135\text{cm}$

Answer 1

The correct option is C $180\text{cm}$

Let the maximum height of a man to see his own image completely in the mirror be $H$.
We know that :
Minimum length of plane mirror to see own complete image
$=\frac{\text{man's height}}{2}=\frac{H}{2}$
$\Rightarrow \text{H}=\text{length of mirror}\times 2$
$H=90\times 2=180\text{cm}$
Option $\left(c\right)$ is the correct answer.