Question

A convex lens of focal length 30cm produces a real image 3 times magnified .Find the object distance.

Answer 1

m=-3

v/u=-3

v=-3u

f=30

¹/f = ¹/v -¹/u

¹/30= -¹/3u-¹/u

¹/30=-⁴/3u

-3u= -4 ×30

u=-4 ×10

u= -40