The power of a lens (biconvex) is \( 1.25 \, \text{m}^{-1} \) in particular medium. Refractive index of the lens is \( 1.5 \) and radii of curvature are \( 20 \, \text{cm} \) and \( 40 \, \text{cm} \) respectively. The refractive index of surrounding medium: