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CBSE Class 12 Physics 2014 Outside Delhi Set 1 Paper

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Question : 15
Total: 30
Two monochromatic rays light are incident normally on the face AB of an isosceles rightangled prism ABC. The refractive indices of the glass prism for the two rays ' 1 ' and ' 2 ' are respectively 1.35 and 1.45 . Trace the path of these rays after entering through the prism.
Solution:  
Critical angle of ray ' 1 ':

sin‌(c1)‌=‌
1
µ1
=‌
1
1.35
c1‌=arc‌ ‌sin(‌
1
1.35
)=47.79∘
Similarly, critical angle of ray '2':

sin‌(c2)‌=‌
1
µ2
=‌
1
1.45
c2‌=sin‌−1(‌
1
1.45
)=43.6∘
Ray ' 1 ' and ' 2 ' will fall on the side AC at an angle of incidence (i) of 45∘. Critical angle of ray ' 1 ' is greater than i, so it will get refracted from the prism. Critical angle of ray ' 2 ' is less than that of i, so it will undergo total internal reflection.
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