Question

an object is placed at a distance of 60 cm from a concave lens of focal length 30 cm . find image distance using lens formula.​ draw ray diagram

Answer 1

Given

object distance, u = 60 cm = - 0.6 m

focal length, f = 30 cm = 0.3 m

since it is a concave lens,

f = - 0.3 m

1/f = 1/v - 1/u

i/v = 1/f + 1/u

v = uf / (f+u) = -0.6 x -0.3 / ( - 0.6 + (-0.3)) = 0.18 / (-0.9) = -0.2 m

image  distance = 20 cm or 0.2 m and image is formed between principal focus and optic center on the same side of the object.