We can calculate the refractive index by following formula: Refractive index of water = Speed of light in vaccum/speed of light in water
The index refraction is the ratio of the speed of light in a vacuum to the speed of light in a substance. It is represented by the letter n and can be found through the equation n = c/v, where c is the speed of light in a vacuum and v is the speed of light in the material.
The index of refraction of a material can also be determined by the formula n = λ0/λn, where λ0 is the wavelength of the light in the vacuum, and λn is the wavelength in the material. The refractive index can also be determined by Snell's Law, which states that n1sinθ1 = n2sinθ2, where n1 and n2 are the indices of refraction in the two media; and θ1 represents the incident ray and θ2 represents the refracted ray. The index of refraction primarily varies with substance and wavelength. Materials of the same composition can have different refractive indices due to the different conditions that they are in. The absorption and reemission of light is different as it travels from atom to atom; thus, it depends on the structure of the atoms composing each material.