Question

A glass has refractive index $3/2$ and water has refractive index $4/3$. If the speed of light in glass is $2 \times 10^8\,m/s $ the speed of light in water in $m/s$ is

• A. $1.5 \times 10^6$
• B. $1.78 \times 10^8$
• C. $2.25 \times 10^8$
• D. $2.67 \times 10^8$

Answer 1

Answer: (C)

Since, $\mu v=$ constant
$ \Rightarrow \mu_{g} v_{g} =\mu_{w} v_{w} $
$\Rightarrow \frac{3}{2}\left(2 \times 10^{8}\right) =\frac{4}{3} v_{w} $
$\Rightarrow v_{w} =2.25 \times 10^{8} m / s$