Question

The graph between $\frac{1}{u}$ and $\frac{1}{v}$ for a thin convex lens in order to determine its focal length is plotted as shown in the figure. The refractive index of lens is $1.5$ and its both the surfaces have same radius of curvature $R$. The value of $R$ will be cm. (where $u=$ object distance, $v=$ image distance)

Answer 1

$f=10cm$

$\frac{1}{f}=(\mu -1)(\frac{1}{R}-\frac{1}{-R})$

$\frac{1}{10}=\frac{1.5-1}{1}\times \frac{2}{R}$

$\frac{1}{10}=\frac{1}{R}$

$R=10cm$