Question

The image of an object formed by amirror is real, inverted and is of magnification -1. if the image is at distance 30 cm of the mirror where is the object placed ?Find the position of the image if the object now moved 20 cm towards mirror?what is the nature of the image obtained ?

Answer 1

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Answer 2

Answer: The image is virtual and image is formed at 30 cm behind the mirror.

Explanation:

Given that,

Magnification m = -1

Distance of the image  v = -30 cm

Using formula of magnification

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

$-1 = -\dfrac{-30}{u}$

$u = -30 cm$

The focal length is

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

$\dfrac{1}{f}=\dfrac{1}{-30}-\dfrac{1}{30}$

$f = -15 cm$

Now, the object moved 20 cm towards mirror

u = -10 cm

Now, the distance of the image

$\dfrac{1}{-15}= \dfrac{1}{v}+\dfrac{1}{-10}$

$\dfrac{1}{v} = \dfrac{1}{30}$

$v = 30$

Hence, The image is virtual and image is formed at 30 cm behind the mirror.