Question

Explain why magnification is negative for real image and positive for virtual image? ​

Answer 1

Answer:

Magnification is the ratio of height of the image(h') to the height of the object(h).

It is also equal to negative of the ratio of the image distance(v) to object distance(u).

Real image is always formed in front of the mirror and virtual image is formed behind the mirror.

Object distance is always negative(according to convention). When the magnification is positive, that means image distance is positive or the image is formed behind the mirror. So it is virtual. And when the magnification is negative, that means image distance is pnegative or the image is formed in front of the mirror. So it is real.

Answer 2

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we know that.....

$magnification = \frac{image \: height}{object \: height}$

Thus.

according to the sign conventions :-

Object is always placed above the principal axis so it will be positive.

but........

for real image

=>but...Real images are always inverted and lie below the principal axis and are thus negative. Therefore, m = - / + = - incase of real images.

and for virtual image

=>Virtual images are always erect and lie above the principal axis and are thus positive. Therefore , m = + / + = + incase of virtual images.

$\huge\mathcal\green{\underline{hope\:\: this\:\: helps\:\: you}}$