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When a fish looks up the surface of a pe...

When a fish looks up the surface of a perfectly smooth lake, the surface appears dark except inside a circular area directly above it. Calculate the angle that this illuminated region subtends. Given `mu` of water `= 1.333`.

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The correct Answer is:
`97.2^(@)`
Here, `mu = 1.333, 2 theta = ?`
`sin C = (1)/(mu) = (1)/(1.333) = 0.75`
`C = sin^(-1)(0.75) = 48.6^(@)`.
Angle which illuminated region subtends
`= 2 theta = 2 C = 2 xx 48.6^(@) = 97.2^(@)`
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