JEE Main | 2014Geometrical OpticsHard
Question
Thin convex lens made from crown glass 
has focal length f. When it is measured in two different liquids having refractive indices 
and 
it has the focal lengths f1 and f2 respectively. The correct relation between the focal lengths is
has focal length f. When it is measured in two different liquids having refractive indices and it has the focal lengths f1 and f2 respectively. The correct relation between the focal lengths is Options
A.f1 = f2 < f
B.f1 > f and f2 becomes negative
C.f2 > f and f1 becomes negative
D.f1 and f2 both become negative
Solution
By Lens maker′s formula
⇒ f1 = 4f & f2 = - 5f
⇒ f1 = 4f & f2 = - 5f
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