Question

Refractive index of glass with respect to medium is $\frac{4}{3}$. If the difference between velocities of light in medium and glass is $6.25\times {10}^{7}m/s$, then velocity of light in medium -

• A. $2.25\times {10}^8$ m/s
• B. $0.125\times {10}^8$ m/s
• C. $1.5\times {10}^7$ m/s
• D. $3\times {10}^7$ m/s

Answer 1

The correct option is A $2.25\times {10}^8$ m/s

${}_m{\mu }_g=\frac{4}{3}$

$\begin{array}{cc}{v}_m-v_g=& 6.25\times {10}^{-7}\\ & v_m=\text{velocity in medium}\end{array}$

${}_m{\mu }_g=\frac{4}{3}=\frac{V_{\text{air}}}{V_{\text{in medium}}}$

$\begin{array}{cc}\frac{4}{3}& =\frac{3\times {10}^8}{v_m}\\ v_m& =\frac{9}{4}\times {10}^8\\ & =2.25\times {10}^{8}m/s\end{array}$