Question

An object is placed at 30 cm in front of a convex lens of focal length 20 cm. Find the position of the image.

Answer 1

convex lens
f=-20
u=-20
lens formula
1/f=1/v-1/u
  1/v=1/f+1/u
       =1/20+1/30
      =3+2/60
     =5/60
  1/v   =1/12
 v=12 cm is answer.

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