Question

an object height 1.2 metre is placed a concave mirror of focal length 20cm so that a real image is formed at a distance of 60 cm from it find the position of an object​

Answer 1

Answer:

$h = 120cm$

$f = - 20cm \: and \: \: v = - 60cm$

$1 \div f - 1 \div v = 1 \div u$

$u = - 2.06 \: \: cm$

position of image is in between focus point and pole

Answer 2

Answer:

u = 30 cm

$\display \text{h _i = 2.4 cm}$

Explanation:

We have given :

Focal length = 20 cm

Image distance =  60 cm

We have to find object distance .

We know :

1 / f = 1 / v + 1 / u

Since image formed is real :

f = - 20 cm and v = - 60 cm

1 / u = 1 - 3 / 60

u = - 30 cm

Hence object distance is 30 cm .

Also given object height = 1.2 cm

We know :

h_i / h_o = - v / u

h_i / 1.2 = - 60 / 20

h_i = - 2.4 cm

Hence image height is 2.4 cm .