At what 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?

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

hi/h= 6/2

hi/h= 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

u = -6.7 cm

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

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  1. Thanks for solution

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