KVPY 2019 SA Exam Previous Papers

Question : 30 of 80

Marks: +1, -0

Four rays, 1, 2, 3 and 4 are incident normally on the face PQ of an isosceles prism PQR with apex angle ∠Q = 120°. The refractive indices of the material of the prism for the above rays 1, 2, 3 and 4 are 1.85, 1,95, 2.05 and 2.15, respectively and the surrounding medium is air. Then the rays emerging from the face QR are :

4 only
1 and 2 only.
3 and 4 only
1, 2, 3 and 4

Validate

Solution:

Given that :

µ_ 1 < µ_2 < µ_3 < µ_4

sin c < sin 30° (for emerging)

1/µ<1/2

µ>2

So, rays 3 and 4 will emerge out

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