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To a bird in air, a fish in water appears to be at 30 ~cm from the surface. If refractive index of water with respect to air is 4 3 , the real distance of bird from the surface is

Options

  1. A60 ~cm
  2. B30 ~cm
  3. C40 ~cm
  4. D50 ~cm

Correct answer

C. 40 ~cm

Step-by-step solution

The correct option is (C). Consider the labeled figure. The fish appears at an apparent depth h๘ while the real depth is h . In triangle OPF : ( i )= P h ( i ) In triangle OPA: ( r )= P h ^ ( r ) For small angles , tam can be taken. Using smell's law of refraction: 1 ( r )= ( i ) Inserting expressions for ( i ) and ( r ) 1 P h ^ = P h h = h ^ Given, h ^ =30 ~cm and = 4 3 , therefore real depth h =40 ~cm .

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