Aadarsh Group Title 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 2 years ago 2 years ago

1. salini Group Title

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

2. Taufique Group Title

$1/f=((\mu2\div \mu1)-1)(1\div R1-1\div R2)$ 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 $f$.

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

@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.