Question

A mirror of focal length 12 cm firms erect image ,3 times the size of obj ..Waht is the distance between obj and mirror​

Answer 1

Answer:

answer =16

Explanation:

Magnification, m = v/u

3 = v/u

⇒ v = 3u

Lens formula : 1/v – 1/u = 1/f

1/3u = 1/u = 1/12

-2/3u = 1/12

⇒ u = -8 cm

V = 3 × (-8) = -24

Distance between object and image = u – v = -8 – (-24) = -8 + 24 = 16 cm

Answer 2

Answer:

16 cm

Explanation:

It's given  that,

magnification = m  = 3 = $\frac{-v}{u}$

So v = 3u

Apply lens formula for convex lens,

$\frac{1}{f} = \frac{1}{u} - \frac{1}{v} \\\\\frac{1}{v} = \frac{1}{u} - \frac{1}{f}$

1 /3u = 1/ u - 1/12

1/u - 1 /3u = 1/12

2/3u = 1/12

u = 2 × 12/3

u = 8 cm

v = 3u

  = 3 * 8

   = 24 cm.

Distance between the object and the image is v - u = 24 - 8 = 16 cm.