Question

A parallel beam of light is allowed to fall on a transparent spherical globe of diameter $30cm$ and refractive index $1.5$. The distance from the centre of the globe at which the beam of light can converge is ______$mm$.

Answer 1

Answer: 225

$\frac{\frac{3}{2}}{V}-\frac{1}{\infty }=\frac{\frac{3}{2}-1}{15}$
$\frac{3}{2V}=\frac{1}{30}$
$V=45cm$
$\frac{1}{V}-\frac{3}{\frac{2}{15}}=\frac{1-\frac{3}{2}}{\frac{2}{-15}}$
$\frac{1}{V}-\frac{1}{10}=\frac{1}{30}$
$\frac{1}{V}=\frac{1}{10}+\frac{1}{30}=\frac{4}{30}$
$V=7.5$
$V=22.5$
$V=225mm$