Question

What is the focal length of a plano-convex lens if 'R' is the radius of curvature and ‘n’ is the refractive index?

• A. $f=R$
• B. $f=\frac R2$
• C. $f=\frac {R}{n-1}$
• D. $f=\frac {n-1}{R}$

Answer 1

Answer: (C)

$f=\frac {R}{n-1}$

Answer 2

The correct option is (C): $f=\frac {R}{n-1}$.