Question

an object of height 1.2 M is placed before 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 what will be the height of the image formed

Answer 1

Height is 1.2m =120cm

Focal length = -20cm
Image distance =-60cm
By using mirror formula
1/u+1/v=1/f
We get u= -15cm
The image is 15cm from the pole of concave mirror
Now we know that h1/h2=-v/u
By putting the value we get h2=-30cm
Height of image is 30cm and inverted

Answer 2

Givent that, ho=1.2m=120cm ,f= -20cm, v=60cm, u=?, hi=?
Using mirror formula
1/v+1/u=1/f
1/60+1/u=-1/20
1/u=-1/20-1/60
1/u=-3-1/60
1/u=-4/60
By cross multiplying we get,
-4u=60
u=-15

m=hi/ho
m=v/u
Therefore hi/ho=v/u
hi/120=60/-15
Again by cross multiplying we get
hi=-7200/15
hi=-480cm or
hi=-4.8m
Hope this helps