Question

An object is placed at a distance of 40 cm in front of a concave mirror of focal length 20 cm. The image produced is:

• A. real, inverted and smaller in size
• B. real, inverted, and of same size
• C. real and erect
• D. virtual and inverted

Answer 1

The correct option is B real, inverted, and of same size

Object distance, $u=-40cm$

Focal length, $f=-20cm$

According to mirror formula,

$\frac{1}{u}+\frac{1}{v}=\frac{1}{f}or\frac{1}{v}=\frac{1}{f}-\frac{1}{u}$

or $\frac{1}{v}+\frac{1}{-20}-\frac{1}{(-40)}=\frac{1}{-20}+\frac{1}{40}$

$\frac{1}{v}=\frac{-2+1}{40}=-\frac{1}{40}orv=-40cm$

Negative sign shows that image is infront of concave mirror.

The image is real.

Magnification, $m=\frac{-v}{u}=-\frac{(-40)}{(-40)}=-1$

The image is of the same size and inverted.