An object of height 1.2m is placed before a concave mirror of focal length 20cm so that a real image is formed at a distance of 60cm from it. Find the position of an object. What will be the height of the image formed?

Academic Physics NCERT Class 10

Given: f = -20 cm; v = -60 cm

To find: Height of the image formed

Solution:

From mirror formula,

$\frac{1}{u}=\frac{1}{f}-\frac{1}{v}$

$\frac{1}{u}=\frac{1}{-20}-\frac{1}{-60}$

$\frac{1}{u}=-\frac{1}{20}+\frac{1}{60}$

$\frac{1}{u}=-\frac{1}{30}$

So u = - 30 cm

Position of an object is 30 cm in front of the mirror

magnification, $m =\frac{h_{i}}{h_{o}} =\frac{-v }{u}$

$h_{i} =\frac{-(-60) }{-30} \times 1.2$

height of image = -2.4 m

Simply Easy Learning

Updated on: 10-Oct-2022

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