Let[R11−R21]=x
f1=[123−1][R11−R21]⇒f=x2
When in liquid 1
f11=[3423−1][R11−R21]⇒f1=x8
When in liquid 2
f21=[3523−1][R11−R21]⇒f2=x−10
A thin convex lens made from crown glass (μ=23) has focal length f. When it is measured in two different liquids having refractive indices 34 and 35, it has the focal lengths f1 and f2 respectively. The correct relation between the focal lengths is :
Held on 6 Apr 2014 · Verified 6 Jul 2026.
f1=f2<f
f1>f and f2 becomes negative
f2>f and f1 becomes negative
f1 and f2 both become negative
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