Question

an object 4 cm tall is placed on the principal axis of a concave mirror of a focal length 20cm at a distance of 30 cm from it find the position nature and size of the image formed​

Answer 1

Height (h) = 4cm
Since it is a concave mirror therefore f = -20cm
Object distance (u) = -30cm
v = ?
h' = ?
By mirror formula...
1/v + 1/u = 1/f
By putting the above values, we get
1/v= 1/f - 1/u
= 1/-20 -(-1/30)
= 1/-20 + 1/30
= 1/30-1/20
= 2-3/60
= -1/60
so
v = -60cm
Also, h'/h = -v/u
So we get h' = -8cm
Therefore, the image is real, inverted and magnified...

Hope it helps.....