Question

An object of size 7cm is placed at 27cm in front of a concave mirror of focal length 18cm. At what distance from the mirror should a screen be placed, so that a sharp focussed image can be obtained?

Answer 1

Dear Student,

Given,
u = -27 cm
h = 7 cm and
f = -18 cm
v = ?

We know that,

1/f = 1/u + 1/v

1/-18 = 1/-27 + 1/v

1/-18 + 1/27 = 1/v

-3+2/54 = 1/v

v = -54 cm

Thus the image is formed at a distance of 54 cm in front of concave mirror(minus sign shows that the image is formed left side of the mirror)

The nature is real and inverted because it is formed in front of the concave mirror.

h₁/h = -v/u

h₁/7 = -54/-27

h₁ = -14 cm

The size of the image is 14 cm and minus sign shows that it is formed infront of the concave mirror.

Regards