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Light Reflection and Refraction
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11/08/2021 1:36 pm
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An object 3 cm high is placed at a distance of 10 cm in front of a converging mirror of focal length 20 cm. Find the position, nature and size of the image formed.
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11/08/2021 1:42 pm
Given: \(h_1\) = 3 cm, u = 10 cm, f = 20 cm
We know that
\(\frac{1}{v}\) + \(\frac{1}{u}\) = \(\frac{1}{f}\)
⇒ \(\frac{1}{v}\) = \(\frac{1}{f}\) - \(\frac{1}{u}\)
= \(\frac{1}{-20}\) - \(\frac{1}{-10}\)
= \(-\frac{1}{20}\) + \(\frac{1}{10}\)
= \(\frac{-1 + 2}{20}\) = \(\frac{1}{20}\)
∴ v = 20 cm
The image is formed at a distance of 20 cm behind the mirror.
And
m = \(-\frac{v}{u}\) = \(\frac{h_2}{h_1}\)
⇒ \(-\frac{20}{-10}\) = \(\frac{h_2}{3}\)
⇒ \(h_2\) = 6 cm
Image is 6 cm in size, virtual and erect.