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Taranpreet Singh from KENDRIYA VIDYALAYA , asked a question
Subject: Science , asked on 27/10/12

define principal focus of a Convex lens and Concave lens

EXPERT ANSWER

Somnath Mazumder ,Meritnation Expert added an answer
Answered on 31/10/12

Principal focus of a convex lens is the point on the principal axis where rays incident parallel to the principal axis will pass through that point after getting refracted by the lens. In the fig. F denotes the principal focus of the lens.

Principal focus of a concave lens is the point on the principal axis where rays incident parallel to the principal axis will appear to diverge from that point when produced behind the lens, after getting refracted by the lens.  In the fig. F denotes the principal focus of the lens.

 

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Taranpreet Singh , From Kendriya Vidyalaya , added an answer
Answered on 28/10/12

is it the same as i mirrors?