Question

an object is kept at 15 cm from a convex lens of focal length 10 cm calculate the image distance and state the characteristics of the image formed

Answer 1

Usee Formula of lens 1/v-1/u=1/f
1/v=1/10+1/-15
1/v=3-2/30=1/30
v=-30cm

Answer 2

u= -15cm....as it is given object distance is 15 cm and object distance is always negative.
f= 10cm
v=?
1/f=1/v-1/u

1/f+1/u=1/v

1/10+1/(-15)=1/v

1/10-1/15=1/v

3-2/30=1/v

1/30=v

v=30cm
m=v/u
30/-15=-2
so , image is real and inverted.