Question

find the nature and focal length of a spherical mirror forming an image at a distance of 10cm from the pole of an object kept at a distance of 30cm​

Answer 1

Answer:

According to mirror formula,

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

So,

$\frac{1}{30} + \frac{1}{10} = \frac{1}{f} \\ \frac{1}{f} = \frac{4}{30} \\ f = 7.5 \: \: cm$

So it is a convex mirror, because focal length of a convex lens is always positive.