Question

The radius of curvature of the convex surface of a plano-convex lens is 10 cm. What is the focal length of the plano-convex lens?(Here, "mu" = 1.5)
a) 10 cm
b) 20 cm
c) 15 cm
d) 5 cm

Answer 1

i dont think r.i is gonna affect the focal length
as R=2f
it is accepted and derived

Answer 2

\[1/f=((\mu2\div \mu1)-1)(1\div R1-1\div R2)\] this is lens maker formula..
here \[\mu1\] is refractive index for air and\[\mu 2\] is the refractive index of the lens(medium).R1 is 10cm and R2 is the infinity(for plane).
put this value in the above equation and find \[f\].

Answer 3

Yeah got it. Thanks a lot. Answer = 20 cm

Answer 4

@salini didi, I found this question in my study material, and "R = 2f" answer did not match the correct option. @Taufique bhaio, ur answer is absolutely correct. Thanks once again.

Answer 5

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3) http://openstudy.com/study?login#/updates/4f7abb4de4b0884e12aac1e7

Answer 6

Post the answers in the respective links itself.