Question

The image of object formed by a mirror is real inverter and is of magnification -1 if the images at a distance of 30 cm from the mirror where is the object placed find the position of the image of the object is now move 20cm towards a mirror what is the nature of the image obtained? justify your answer with the help of a diagram

Answer 1

as m = -1, -v/u = -1, v = u, object is placed at 30 cm.

as object is moved 20 cm towards mirror, then u = 10 cm < f = 15 cm.

nature of image is virtual, erect and enlarged.

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.