Question

The velocities of light in two different media are 2 x 10${}^8$ ms${}^{-1}$ and 3.5 x 10${}^8$ ms${}^{-1}$ respectively. The critical angle for these media is :

• A. $si{n}^{-1}$(1/5)
• B. $si{n}^{-1}$(4/7)
• C. $si{n}^{-1}$(2/3)
• D. $si{n}^{-1}$(6/7)

Answer 1

The correct option is B $si{n}^{-1}$(4/7)

$\mu =\frac{v_2}{v_1}=\frac{3.5}{2}=1.75$

${\theta }_{cric}=si{n}^{-1}\left(\frac{1}{\mu }\right)=si{n}^{-1}\left(\frac{1}{1.75}\right)=si{n}^{-1}\left(4/7\right)$