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Grade 12Wave Optics

the focal length of a plano-concave lens is -10cm, then its focal length when its plane surface is polished is?

Profile image of vaanya
12 Years agoGrade 12
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3 Answers

Profile image of Nirmal Singh.
12 Years ago
When Plane surface is polished then it bahave like a concave mirror and it focal length will be - 10 cm

Regards,
NIrmal Singh
Askiitians Faculty
Profile image of vaanya
12 Years ago
the answer is +5cm. plz tell me how to solve it.
Profile image of Kajal
7 Years ago
Any lens + plane mirror = -1/2 (f)
=-1/2 (-10)
=+5 
=Ans
its ans shortcut by our physics teacher , don't tell him that i have leaked this awesome shortcut!! :)

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