The absolute refractive index of glass and water are 3/2 and 4/3, respectively. If the speed of light in glass is 2×10⁸ m/s, calculate the speed of light in: (a) vacuum (b) water

Given : nwater=4/3, nglass=3/2, vglass=2×10⁸ m/s, nair=1
Speed of light in a medium vmedium=c/n where c and n are the speed of light in vacuum and refractive index of medium respectively
(a) : vglass=c/nglass
∴2×10⁸=c(3/2)
∴c=3×10⁸ m/s
(b) : vwater=c/nwater
∴vwater=3×10⁸(4/3)=2.26×10⁸ m/s