Question

14. When an object is placed at a distance of 15 cm from a concave mirror, its image is formed at 10 cm in front
of the mirror. Calculate the focal length of the mirror.​

Answer 1

Answer:

Question :–

When an object is placed at a distance of 15 cm from a concave mirror, its image is formed at 10 cm in front of the mirror. Calculate the focal length of the mirror.

Given :–

u = -15 cm

v = -10 cm

To Find :–

Focal length of the mirror.

Solution :–

We know that,

$→ \frac{1}{v} + \frac{1}{u} = \frac{1}{f}→v1+u1=f1$

$→ \frac{1}{ - 10} + \frac{1}{ - 15} = \frac{1}{f}→−101+−151=f1$

$→ - \frac{1}{10} - \frac{1}{15}→−101−151$

We have to find L.C.M. of the denominators,

★ L.C.M. is refer to the attachment ★

$→ \frac{ - 3 - 2}{30 }→30−3−2$

$→ - \frac{ \cancel5}{\cancel{30}}→−305$

$→ - \frac{1}{6}→−61$

Therefore,

f = -6 cm

Hence,

,The focal length of the mirror is 6 cm.