Question

17.When an object is placed 20cm from a concave mirror, a real image magnified three times is formed. a)find the image distance b)focal length

Answer 1

GIVEN THAT ---》

object distance ( U ) = - 20 cm

Maginification = -3

To FIND ---》 Image distance ( I ) = ?

Focal length = ?

a ) By Magnification Formulae ,

M = - V / U

- 3 = - V / - 20

V = - 60 cm.

b ) By Mirror's Formulae ,

1 / F = 1 / V + 1 / U

1 / F = 1 / - 60 - 1 / 20

1 / F = { -1 + ( - 3 ) } / 60

1 / F = -4 / 60

1 / F = - 1 / 15

F = - 15 cm

image distance is - 60 cm and focal length of concave mirror is - 15 cm

hoped so u got the ans...thnks a lot for asking