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Question
Find the angle of incidence at face AB so that the emergent ray grazes along the face AC.
Solution
from snell's law we know that
`sini/sinr =μ_(12)`
For the emergent ray to graze at the face AC, the angle of refraction should be 90°.
So, applying snell's law at face AC, we get `(sini_(AC)/sinr_(AC) )= μ_(21)`
`⇒ (sin i_(AC)/sin 90^@)=1/sqrt2 or i_(AC)= 45°.`
From geometry we can see that angle of refraction at face AB is 15°.
So applying snell's law we get `(sin i_(AB)/sin r_(AB))= μ_(12)`
`or sin i_(AB) = sin r_(AB)×μ_(12)`
`or i_(AB) =sin^-1(sqrt2sin15°)`
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