Question

A dentist uses a small concave mirror of focal length 3 cm and hold it at a distance of 2 cm from the tooth. Which of the following statement is incorrect about the image formed?

Answer 1

Given :
Focal length, $f=-3cm$
Object distance, $u=-2cm$

Using mirror formula,
$\frac{1}{\text{f}}=\frac{1}{\text{v}}+\frac{1}{\text{u}}$
$\frac{1}{\text{-3}}=\frac{1}{\text{v}}+\frac{1}{\text{-2}}$
$v=6cm$
Hence, the image distance (v) is +6cm from the pole of the mirror.
Also, the distance between the object and the image is,
D = 6 cm + 2 cm = 8 cm

$Magnification=\frac{h_i}{h_o}-\frac{v}{u}=-\frac{6}{-2}=3$

Thus, Image formed is three times of the object size and it is virtual and erect.

Hence option B is incorrect.