Refractive Index of the medium is the ratio of _____.

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ALP CBT 2 Electronic Mechanic Previous Paper: Held on 21 Jan 2019 Shift 2
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  1. Velocity of light in the medium to the Velocity of light in the vacuum
  2. Velocity of light in water to the velocity of light in air 
  3. Velocity of light in the water to the velocity of light in the vacuum
  4. Velocity of light in the vacuum to the velocity of light in the medium 

Answer (Detailed Solution Below)

Option 4 : Velocity of light in the vacuum to the velocity of light in the medium 
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Refractive index: The ratio of the speed of light in a vacuum to speed of light in a medium is called the refractive index of that medium. It is also called an absolute refractive index.

\({\rm{Refractive\;index\;}}\left( \mu \right) = {\rm{\;\;}}\frac{{Speed\;of\;light\;in\;vaccum\left( C \right)}}{{Speed\;of\;light\;in\;a\;medium\left( v \right)}}\)

Relative refractive index: When a light ray is going from one medium (other than vacuum) to another medium then the value of the refractive index is said to be a relative refractive index.

\({\rm{Refractive\;index\;of\;medium\;}}1{\rm{\;with\;respect\;to\;medium\;}}2{(n_{21})} = {\rm{\;}}\frac{{\;refractive\;index\;of\;medium\;1 {(n_1)}}}{{\;Refractive\;index\;of\;medium\;2{(n_2)}}}\)

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