Question

A 1.2cm long pin is placed perpenducular to the principle axis of a convex mirror of focal length 12 cm,at a distance of 8cm from it.the location of image is at

Answer 1

Given :

h1 = +1.2 cm
f = +12 cm
u = -8 cm

Using mirror formula ;

(1/f) = (1/v) + (1/u)

(1/12) = (1/v) + (1/-8)

1/v = (1/12) + (1/8)

1/v = (2+3)/24

v = 24/5

v = +4.8 cm
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m = h2/h1 = -v/u

h2 = (-4.8/-8) × 1.2

h2 = + 0.72 cm
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Hence the image formed is Virtual and erect of size 0.72 cm and at a distance of 4.8 cm from the mirror.
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Answer 2

Given,

Hight of the object = 1.2 cm

Focal length = +12cm

object distance =-8cm

According to mirror formula,

1/f = 1/v + 1/u

or, 1/12 = 1/v - 1/8

or, 1/v = 1/12 + 1/8

or, 1/v = 2+3 / 24

or, v = 24/5

or, v = +4.8

So the distance of the image is +4.8cm

The positive sign shows that the image is formed on the other side of the optical centre.

Hope it helps.