Question

An object is placed at a large distance in front of a concave mirror of radius of curvature 60 cm. The image will be formed in front of the mirror at a distance of :; A. 20 cm; B. 30 cm; C. 40 cm; D. 50 cm

Answer 1

Answer:

B. 30 cm

Explanation:

As given in the question,

the radius of curvature of the concave mirror, R = 60 cm

Hence, the focal length of the given concave mirror is given by,

$f\ =\ \dfrac{R}{2}$

   $=\ \dfrac{60}{2}$

   = 30 cm

Since the object is placed at a large distance from the mirror, hence we can assume the distance of the object from the mirror is infinity.

Now according to mirror formula,

   $\dfrac{1}{v}\ +\ \dfrac{1}{u}\ =\ \dfrac{1}{f}$

whrere, u = object distance from mirror

              v = image distance from mirror

$=>\ \dfrac{1}{v}\ +\ \dfrac{1}{\infty}\ =\ \dfrac{1}{30}$

$=>\ \dfrac{1}{v}\ =\ \dfrac{1}{30}$

$=>\ v\ =\ 30 cm$

So, the image will be formed at 30 cm in front of mirror.