• # question_answer An equiconvex lens has a power of 5 diopter. If it is made of glass of refractive index 1.5 then the radius of the curvature of each surface will be A) 20 cm B) 10 cm   C) 5 cm D) zero

[a] The focal length of an equiconvex lens is given by $\frac{1}{f}=\frac{2(\mu -1)}{R}$. It is given that $\frac{1}{f}=+5$ and $\mu =1.5$. Therefore, $5=\frac{2(1.5-1)}{R}$ or $R=\frac{1}{5}$ metre = 20 cm