Question

calculate the distance at which an object should be placed in front of a convex lens of focal length hundred cm to obtain An erect image of double its size​

Answer 1

Answer:

-50 cm

Explanation:

Given convex lens, f = 100 cm, virtual and erect image, m = 2

Since image is virtual and erect, m = +2

as m = v/u,

2 = v/u

v = 2u

By lens formula, 1/f = 1/v - 1/u

So 1/100 = 1/2u - 1/u

1/100 = 1/2u - 2/2u

1/100 = -1/2u

100 = -2u

u = -50 cm

Therefore the object should be placed at -50 cm.

Hope it helps!!