Question

at what diatance from concave mirror of focal length 10 cm should an object 2 cm long be placed in order to get an erect image 6 cm​

Answer 1

Given

Focal length of concave mirror f = -10 cm

Height of the object ho = 2 cm

Height of the image hi = 6 cm

We need to find the object distance

So we know that

Magnification m = hi/ho = 6/2 = 3 (erect image)

m = -v/u

3 = -v/u

⇒ v = -3u

Let us now consider

Mirror formula: 1/v + 1/u = 1/f

1/(-3u) + 1/u = 1/(-10)

⇒ u = -20/3 = -6.7 cm

So At -6.7cm distance from a concave mirror of focal length 10cm should an object 2cm long be placed in order to get an erect image 6cm tall.

Answer 2

Explanation:

-6.7 is the answer

Hope it is helpful.