Question

If the refractive index of water is $\frac{4}{3}$, the velocity of light in vacuum is $3\times {10}^{10}$ cm/sec. The time required to travel a distance of $450cm$ in water will be :

• A. $0.2\mu$ s
• B. $0.02\mu$ s
• C. $2\mu$ s
• D. $2000\mu$ s

Answer 1

The correct option is B $0.02\mu$ s

Using snell's law,
$\frac{sini}{sinr}=\frac{v_1}{v_2}=\frac{{\mu }_2}{{\mu }_1}$

So $v_1{\mu }_1=v_2{\mu }_2=v_2{\mu }_2$

$⟹3\times {10}^{10}\times 1=\frac{450}{t}\times \frac{4}{3}$
$t=0.02\mu s$