LAWS OF REFRACTION:



(i) The incident ray, there fracted ray and the normal to the refracting surface at the point of incidence, all lie in the same plane.



(ii)The ratio of sine of the angle of incidence to the sine of the angle of refraction is constant for any two given media

i.e. = constant = 1µ₂ = Refractive index.

This is called Snell's law.





Refractive index:



• 1µ₂ = then 1µ₂ (or ₁n₂) is a constant called refractive index of the second medium w.r.t. first medium (containing incident ray)



• 1µ₂ =    where µ₂ is absolute refractive index of second medium and µ₁ is of first.



• Refractive index is a relative quantity. If the first medium is air (vaccum to be precise) then = µ or n called absolute refractive index.



      =>  µ₁ sin i = µ₂ sin r = constant.

product of absolute R % of medium and sine of rays with normal in that medium is constant.





Dumb Question: What actually occurs in the process of refraction and what is true significances of µ ?



Ans: During refraction, the velocity of light changes at the interface and thus light follows an alternative path.

µ is actually ratio of light in vaccum with the speed of light in given medium

µ      1µ₂ =





Dumb Question: What parameter of wave changes during refraction.



Ans: During the process of refraction only frequency of light remains constant, while wavelength and velocity change







Dumb Question: What is the meaning of 'rare' and 'dense' when associated with medium ?



Ans: 'rare' and 'dense' are also relative terms. When compared the medium with higher value of refractive index is called 'denser medium' and the other one is called rarer medium.

Dense medium is the one in which light travels slower than in rarer medium.

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