The speed of light in a medium whose critical angle is 60° will be

$2.6 × 10^8 m/s$

The correct answer is Option (1) → $2.6 × 10^8 m/s$

The relationship between the critical angle & refractive indices (μ) is -

$\sin θ_c=\frac{μ_2}{μ_1}$

$⇒\sin 60°=\frac{1}{μ_1}⇒μ_1=\frac{2}{\sqrt{3}}≃1.555$

and,

Speed of light, $v=\frac{c}{μ_1}=\frac{3×10^8}{1.555}$

$≃2.6×10^8m/s$