Question

a converging mirror forms a three times magnified virtual image when the object is placed at a distance of 8cm from it calculate the focal length

Answer 1

U=-8cm m=+3
Now, m=-v/u
-v=m*u
-v=3(-8)=-24
v=24cm

So,
1/f=1/v+1/u
1/f=1/24+1/-8
=1/24-1/8
=1-3/24
=-2/24
=1/-12
f=-12cm

Hope it helps you dear .....