Question

A concave length have focal length 15cm. At what distance the object should be placed so it forms an image of 10cm from lens and find magnification

Answer 1

GIVEN :
focal length =f=-15 cm after sign conventions
image distance=V=-10cm
object distance=?
by lens formula:
1/f=1/v-1/u
1/u=1/v-1/f
= -1/10+1/15
= -3+2/30
=-1/30
u=-30cm
Magnification=m=v/u
=-10/-30=1/3=0.33