Question

The image formed by a spherical mirror is real and inverted and is of magnification -2.If the image is at a distance of 30 cm from the mirror, where is the object placed? Find the focal length of the mirror

Answer 1

magnification=-v/u
-2= -(-30)/u
-2=30/u
u=-30/2
u=-15
so we use mirror formula
and then we get solution of this question

Answer 2

Answer:

Given :

Magnification m = - 2

Image distance v = 30 cm

We know :

m = - v / u

- 2 =  - (- 30 ) / u

u = - 15 cm

We have mirror formula :

1 / f = 1 / v + 1 / u

1 / f = 1 / - 15 - 1 / 30

1 / f = - 1 / 10

f = - 10 cm

When the object is moved 10 cm towards the mirror.

Then : u' = u - 10 cm

= > u' = - 5 cm

Again putting in formula to get v'

1 /  - 10 + 1 / 5 = 1 / v'

1 / v' = 2 - 1 / 10

v' = 10 cm

Therefore , the image is located 10 cm behind the mirror.

Also new magnification :

m' = -v' / u'

m' = - 10 / -5

m' = 2

Since magnification is positive the image is erect and virtual.

Also image is magnified in nature.