Question

The focal length of a concave mirror is 50 cm. Where an object be placed so that its image is two times and inverted?

• A. 75cm
• B. 72cm
• C. 63 cm
• D. 50 cm

Answer 1

Answer: (A)

. 75 cm.

Given,

Focal length of a concave mirror = $f=-50cm$

Magnification = $m=-2$ (Since image is inverted)

We know that, magnification = $m=-\frac{v}{u}$.........(i)

mirror formula, $\frac{1}{f}=\frac{1}{v}+\frac{1}{u}$......(ii)

From equation (i) and (ii), we get

$m=\frac{f}{f-u}$

$\Rightarrow -2=\frac{-50}{-50-u}$

$\Rightarrow u=-75cm$.