If in a plano-convex lens radius of curvature of convex surface is 10 cm and the focal length of the lens is 30cm, the refractive index of the material of the lens will be:
1.33
f = 30 cm
R0 = 10 c
1f=(n−1)(1R1 - 1R2)
130=(n−1)(1∞−(1−10))
⇒n−1=13
⇒n=43=1.33