Question

At what distance from a convex lens of focal length 30 cm, an object should be placed so that the size of the image be 1/2th of the object

Answer 1

Answer:

m = -v/u

⇒-v = mu

⇒-v = (1/2)(30)

⇒-v = 15cm

⇒v = -15

The object should be placed 15 cm in front of the mirror.

Answer 2

Answer:

15 cm

Explanation:

We will first use the formula of magnification.

m=$\frac{-v}{u}$

$\frac{1}{2} =\frac{-v}{-30}$ (By cartesian signs)

$\frac{1}{2}$×$30=v$

v=15 cm