The refractive index of the material of crystal is 1.68 and that of castor oil is 1.2. When a ray of light passes from oil to glass, its velocity will change by factor

Step-by-step solution

We know, refractive index of crystal w. r. t. oil, μ c o = μ c μ o = s p e e d o f l i g h t i n o i l s p e e d o f l i g h t i n c r y s t a l Where, μ c = absolute refractive index of crystal w. r. t. vacuum. and μ 0 = absolute refractive index of oil w. r. t. vacuum. μ c o = 1.68 1.2 7 5 = s p e e d i n o i l s p e e d i n c r y s t a l Fractional change in velocity, when light travel from oil to crystal = s p e e d i n c r y s t a l s p e e d i n o i l = 5 7