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Wave Optics

Question
CBSEENPH12038321

For a ray of light travelling from a denser, medium of refractive index n1 to a rarer medium of refractive index n2. Prove that n/ n1= sin ic where ic is the critical angle of incidence for the media.

Solution

Given, a ray of light travelling from denser medium of refractive index n1 to a rarer medium of refractive index n2. 
Snell's law is given by,
  
                       sin isin r = n2n1

Now, critical angle is the angle of incidence in denser medium for which angle of refraction in rarer medium is 90o
i.e.,    i = ic  when r = 90o

Thus, putting these values in snell's law , we have 

                    sin icsin 90o = n2n1 
 
i.e.,                      n2n1 = sin ic 
 

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