Question

An object of height 1.2 cm is placed at a distance of centimetre from the optical centre of a cocave mirror
of focal length 20 centimetre
to find the position and size of the image formed mark optical Centre O and find the image of India find the height of image in that diagram

Answer 1

height of object = 1.2 cmObject is always place to the left side of a mirror therefore the object distance (u) is always negative.
If the image is formed in front of the mirror(real image) on the left side then the image distance (v) will be negative.
The focus of concave mirror is in front of the mirror on the left side so the focal length of a concave mirror is considered negative.
Given:
Focal length (f)= -20 cm ( concave mirror)
Image distance (v)= -60cm (real image)
Height of the object (h1)= 1.2cm
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= -2/60= -1/30
1/u= -1/30 
u = -30
Object distance(u) = -30 cm
Magnification (m) = -v/u
m = - (-60) /-30= 60/-30= -2
m = h2/h1
-2= h2/1.2
-2×1.2= h2
h2= -2.4 cm
Height of real image (h2)= -2.4 cm
Real image is formed below the axis. So the height of a real image is negative.
Hence, the position of an object is -30 cm(to the left of mirror) & the height of the real image formed is -2.4 cm
HOPE IT WILL HELP ^_^