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CBSE Class 12 Physics 2022 Term 2 Delhi Set 1 Solved Paper

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Question : 10
Total: 12
A ray of light passes through a prism of refractive index √2 as shown in the figure. Find: 3

(i) The angle of incidence (∠r2) at face AC.
(ii) The angle of minimum deviation for this prism.
Solution:  
(i) Since at point N, the angle of reflection is 90°, then ∠r2 is the critica angle for the glass - air pair of media.
sin∠r2=
1
μ
=
1
√2
∠r2=sin−1(
1
√2
)=45°
(ii) μ=
sin(A+
δm
2
)
sin
A
2

Or, √2=
sin(60°+
δm
2
)
sin
60°
2

Or, √2=
sin(30°+
δm
2
)
1
2
Or, 0.7=sin(30°+
δm
2
)
Or, sin−10.7=30°+
δm
2
Or, 44.4°=30°+
δm
2
∴δm=28.8°
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