Question

Example 10.2
An object, 4.0 cm in size, is keep at 25.0 cm in
front of a concave mirror of focal length 10.0
cm. At what distance from the mirror should
a screen be located in order to get a sharp
image? Find the size and the nature of the
image.​

Answer 1

Answer:

object distance (u)= -25cm

Focal length f = -10cm

By mirror formula

1/f = 1/v + 1/u

i.e. 1/v = 1/-10 + 1/-25

i.e. 1/v = (-5 -2)/50

i.e. v =- 50/7

i.e. v = -7.14cm

By magnification,

m= -v/u

i.e. h'/h = -v/u

i.e. h'/4 = -50/175

i.e. h' = -200/175

i.e. h' = -1.14cm

Therefore the height of object is 1.14cm (approx.)

and as image is on same side of object and height is in negative, therefore image formed is real and inverted