An object is placed at the focus of a convex mirror. If its focal length is 20 cm, the distance of mirror is

Question

An object is placed at the focus of a convex mirror. If its focal length is 20 cm, the distance of mirror is (A) 20 cm (B) 10 cm (C) 40 cm (D) None of these

Tardigrade Admin · Accepted Answer

f is +ve for convex mirror. Therefore, for convex mirror (1/v)-(1/20) =+(1/20) (1/v) =(1/10) or v =10 cm

Q. An object is placed at the focus of a convex mirror. If its focal length is $20 c m,$ the distance of mirror is

20 cm

10 cm

40 cm

None of these

$f$ is +ve for convex mirror.
Therefore, for convex mirror
$\frac{1}{v} - \frac{1}{20} = + \frac{1}{20}$
$\frac{1}{v} = \frac{1}{10}$
or $v = 10 c m$

Q. An object is placed at the focus of a convex mirror. If its focal length is 20cm, the distance of mirror is