Consider an equiconvex lens of radius of curvature R and focal length f. If f > R, the refractive index μ of the material of the lens.
1f=(μ−1)(2R)
orf=R2(μ−1)
Now,f>R
∴R2(μ−1)>R
or12(μ−1)>1or2(μ−1)<1
orμ−1<12orμ<(1+12)orμ<1.5
Why this question? Caution: Refractive index for any medium cannot be less than 1. |