A thin-plano convex lens acts like a concave mirror of 28cm focal length when is plane surface is silvered.Calculate the radius of curvature of its curved surface if the refractive index of the material of the lens s 1.5 and also find the power of the lens

Dear Ayush,

n1/u +n2/v=(n2-n1)/r

for first refraction by convex surface: u→∞, v=rn2/(n2-n1)

for plane reflection: r is infinite,v'=-v

for second refraction: 1.5/v' -1/v''=(1-1.5)/r

1/v''+1/v=1/f

power=1/f

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