Optics Question 990

Question: A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is $ \frac{4}{3} $ and the fish is 12 cm below the surface, the radius of this circle in cm is

[NCERT 1980; KCET 2002; AIEEE 2005; CPMT 2005]

Options:

A) $ 36\sqrt{5} $

B) $ 4\sqrt{5} $

C) $ 36\sqrt{7} $

D) $ 36/\sqrt{7} $

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Answer:

Correct Answer: D

Solution:

$ r=\frac{3h}{\sqrt{7}}=\frac{3\times 12}{\sqrt{7}}=\frac{36}{\sqrt{7}} $ .



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