Question

a concave mirror for face viewing has focal length of 0.4 m.the distance at which you hold the mirror from your face in order to see your image upright with a magnification of 5 is​

Answer 1

Answer: 32 cm

Refer to the following explanation.

Answer 2

The distance at which you hold the mirror from your face is 32 cm.

Explanation:

It is given that,

Focal length of the concave mirror, f = -0.4 m = 40 cm

Magnification of the object, m = 5

We know that the magnification of the mirror is given by :

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

v is the image distance

u is the object distance

$5=\dfrac{-v}{u}$

$\dfrac{1}{v}=\dfrac{-1}{5u}$

Using mirrors formula as :

$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}$

$\dfrac{1}{-40}=\dfrac{-1}{5u}+\dfrac{1}{u}$

$\dfrac{1}{-40}=\dfrac{4}{5u}$

u = -32 cm

So, the distance at which you hold the mirror from your face is 32 cm. Hence, this is the required solution.

Learn more,

Mirror's formula

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