Refractive indexSpeed of light in vacuum=\xa03.00×108\xa0m/s.The amount of change in speed of light in a medium depend upon the property of medium(refractive index)Refractive index\xa0is a measure of how much speed of light changes when it enter the medium from air.Absolute refractive index\xa0is the ratio of speed of light in vacuum or air to speed of light in the medium. cn=—— νRelative refractive index Speed of light in medium 1n21\xa0= ————————————– Speed of light in medium 2Refractive index of medium 2 wrt medium 1 is known as refractive index of medium 2. Speed of light in medium 2n12= ————————————– Speed of light in medium 1Refractive index of medium 1 wrt medium 2 is known as refractive index of medium 1.1)When light goes from rarer medium to denser medium.\xa0Sin i n1——- = —— >1\xa0\xa0\xa0Sin r n2Sin i >Sin r∠i=∠rReflected ray bend toward normal.2)When light goes from denser medium to rarer medium.Sin i n2——- = ——- <1sin r n1\xa0Sin i < Sin r∠i <\xa0∠rReflected ray bend away from the normal.Refractive index depend on nature of material of medium,density of medium,colour or wavelength of light.