Question

a concave lens has focal length of 15 cm at what distance should the objective from and the lens be place so it forms an image at 10 cm from the lens? also find the magnification produced by the lens​

Answer 1

F= -15

V = -10

1/f= 1/v -1/u

1/u= -1/10-1/15

1/u = -5/30

1/u = -1/6

u= -6

The object is placed at a dist of 6 cm from the lens

Magnification =m= v/u = -10/-6 = 1.67

Answer 2

$\huge\boxed{\underline{\mathcal{\red{A}\green{N}\pink{S}\orange{W}\blue{E}\pink{R}}}}$

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