Question

Light travels with a speed of $2\times {10}^{8}m/s$ in crown glass of refractive index 1.5, what is the speed of light in dense flint glass of refractive index 1.8

• A. $1.33\times {10}^{8}m/s$
• B. $1.67\times {10}^{8}m/s$
• C. $2.0\times {10}^{8}m/s$
• D. $3.0\times {10}^{8}m/s$

Answer 1

The correct option is B $1.67\times {10}^{8}m/s$

$\begin{array}{c}\text{Uerownglass}=1.5\end{array}\text{, Verownglass =}2\times {10}^8{ms}^{-1}\text{Uerownglass}=1.8$

$\begin{array}{cc}\frac{V_{\text{crownglass}}}{v_{\text{flint glass}}}& =\frac{{\mu }_{f\text{lint glass}}}{{\mu }_{\text{crow glass}}}\\ \Rightarrow v_{\text{fint glass}}& =\frac{2\times {10}^8\times 1.5}{1.88}\\ & =1.67\times {10}^8{ms}^{-1}\end{array}$