Question

The image formed by plane mirror is real and inverted and is of magnification -1. If the image is at the distance of 30cm from the mirror where is the object placed?

Answer 1

Real image means that if you put a screen at the image oint you will see the object projected on the screen.

However, if you do not use a screen but look at the real image, you actually see the light rays coming from the mirror and you assume that the image is behind the mirror.

This also applies in the plane mirror; we perceive the image to be behind the mirror since we get the light rays reflected/coming from the mirror.

Answer 2

Answer:

+ 30 cm

Explanation:

Given :

Magnification = - 1

Image distance = 30 cm

We know

m = - v / u

- 1 = 30 / u

u = - 30 cm

Now we have ,

1 / f = 1 / v + 1 / u

1 /  f = 1 / - 30 - 1 / 30

f = - 15 cm

When object moved 20 cm

u' = - 30 + 20 = - 10 cm

We have f = - 15 cm

We have to find new image distance v'

Again ,

1 / f = 1 / v' + 1 / u'

- 1 / 15 = 1 / v' - 1 / 10

1 / v' = 1 / 30

v' = 30.

Nature of image as :

Virtual

Erect

Magnified.