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ankitasingh (0)

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a fish rising vertically to the surface of a lake at 3m/s observes a bird diving vertically downat the rate of 9m/s. what is the actual velocity of the bird?
    
malay (134)

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since this situation deals with normal incidence of light on the water air- interrface, no phenomena of refraction will occur.
hence actual velocity of bird=9-3=6m/s downwards

Imagination is more important than knowledge
-------Albert Einsetein
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rahul_c (188)

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refractive index (n) = apparent depth/real depth

if displacement with respect to unit time is taken = (9/n)

actual velocity= (9/n) - 3

n is the refractive index of water

The yardstick of human intelligence is the ability to overcome the last fallacy
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AAKRITI (228)

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The answer will be 6/n :
In fish frame; vb,f = vf + nvb

you have to run faster and faster so as to remain where you are.. even if you are on the right track you will get run over if you just keep sitting there...
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you_saket (0)

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what is the esay way to solve  numarical of refractive index through prism.
 
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mohit1 (0)

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krishna.gopal (2037)

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If velocity of bird is v it wil appear 1.33v to an stationary fish (refractive index of water is 1.33).
1.33v+3=9
v=6/1.33
 
So Aakriti's answer is right

Krishna Gopal Singh
B.Tech Chemical Engg
IIT Delhi 2002
Currently doing PhD from IIT Delhi
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