What is meant by refractive index? If the speed of light in a medium is 2/3rd of the speed of light in vacuum, find the refractive index of that medium.
Refractive index is the measure of bending of ray of light as it passes from one medium to another. It is also defined as the ratio of the speed of light in vacuum to the speed of light in any medium.
Refractive index (μ) = 
Given
Speed of light in a medium (v) = 
⇒ 
⇒ μ = 
⇒ μ = 
Hence Refractive index of medium is 1.5.
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