Question

A concave mirror forms a real image at 15.0 cm from the mirror surface along the principal axis. If the corresponding object is at a distance of 30.0 cm, what is the mirror's focal length? Please show your work

Answer 1

Answer:

Focal length, f = 10 cm

Explanation:

We have,

A concave mirror forms a real image at 15.0 cm from the mirror surface along the principal axis, it means that the image distance is 15 cm

The object is placed at a distance of 30 cm, u = -30 cm

It is required to find the focal length of the mirror. Let it is f. Using mirror's formula to find it:

$\dfrac{1}{v}-\dfrac{1}{u}=\dfrac{1}{f}\\\\\dfrac{1}{15}-\dfrac{1}{(-30)}=\dfrac{1}{f}\\\\f=10\ cm$

So, the focal length of the mirror is 10 cm.