spherical convex surface separates object and image space of refractive index 1 and 4/3 respectively. If radius of curvature of the surface is 0.1 m, its power is :

2.5 D −2.5 D 3.3 D −3.3 D

2.5 D

For a single spherical surface $\frac{μ_2}{f}=\frac{μ_2-μ_1}{R}$ $⇒P=\frac{μ_2-μ_1}{μ_2R}$ putting the values, P = 2.5 D.