Question

A conver lens forms a real image
at a distance of 18 cm when an
object is at 9 cm from its optic
centre. What is it's focal length?

plz answer fast thank you!!!!!​

Answer 1

Explanation:

f=-18

1/f=1/v+1 /u

1/f=1/18+(-1/9)

=1-2/18

=-1/18

f=-18