P1=(n−1)(R1−−R1)
P1=(n−1)R2 .........(1)
1.5P1=(n−1)(R1−∞1) .......(ii)
3P2=Rn−1
From (i) and (ii)
23=2RR′
⇒ R′=3R
A double convex lens has power P and same radii of curvature r of both the surfaces. The radius of curvature of a surface of a plano-convex lens made of the same material with power 1.5P is :
Held on 6 Sept 2020 · Verified 6 Jul 2026.
2R
2R
23R
3R
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