Question

A spherical convex surface separates object and image spaces of refractive indices $1.0$ and $4/3$. If radius of curvature of the surface is $10cm$, find its power.

• A. $3.5D$
• B. $2.5D$
• C. $25D$
• D. $1.5D$

Answer 1

The correct option is B $2.5D$

For refraction at a spherical surface,

$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$

$Power=1/f=1/v(withu=-\infty$)

Therefore power $=\frac{{\mu }_2-{\mu }_1}{{\mu }_{2}R}$

$=\frac{\frac{4}{3}-1}{\frac{4}{3}\times 0.1}$

$=2.5D$