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A thin convex lens of focal length 10 cm is placed over a plane glass mirror. An object is placed 20 cm above the lens.Find the distance of image from the object.

A thin convex lens of focal length 10 cm is placed over a plane glass mirror. An object is placed 20 cm above the lens.Find the distance of image from the object.

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1 Answers

Askiitians Expert Soumyajit IIT-Kharagpur
28 Points
12 years ago

Dear Ajit,

The image distance after 1st refraction by the lens is=20 cm towards the plane mirror (simply from the lens formulae)

but it will get reflected from the mirror and will try to form at a distance 20 cm in front of the lens. it will then again rf\efracted by the lens and this time u=+20 cm

So again using lens formulae we get, v=20/3 cm from the lens towards the object.

Hence the distance between the image & the object will be=(20 - 20/3)cm

                                                                               =40/3 cm

 

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SOUMYAJIT IIT_KHARAGPUR

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