Critical angle for total internal reflection \\\\(\ heta_c = 30^o\\\\)As we know, refractive index of air medium \\\\(n_{air} = 1\\\\)Refractive index of the medium \\\\(n = \\dfrac{1}{\\sin\ heta_c}\\\\)\\\\(\ herefore\\\\) \\\\(n = \\dfrac{1}{\\sin 30^o} = \\dfrac{1}{0.5}\\\\)\\\\(\\implies\\\\) \\\\(n = 2\\\\)Velocity of light in medium \\\\(v = \\dfrac{c}{n}\\\\)\\\\(\ herefore\\\\) \\\\(v = \\dfrac{3\ imes 10^8}{2} = 1.5 \ imes 10^8 m/s\\\\)