A fish rising vertically to the surface of water in a lake uniformly at the rate of 3m/s observes a kingfisher diving vertically towards the water at a rate of 9m/s vertically above it. If the R.I. of water is 4/3, find the actual velocity of dive of bird.

Question

experimentx · Answer

looks like question is related to "related rates"

ujjwal · Answer

And refraction.. + a lot of logic.. I guess..

vincent-lyon.fr · Answer

Is the answer 8 m/s ? or 4.5 m/s ?
I am not so sure of the relation for the plane boundary.

ujjwal · Answer

its 4.5 m/s

ujjwal · Answer

i got 8 m/s

experimentx · Answer

looks like the actual height is less than observed height!!

vincent-lyon.fr · Answer

Velocity of virtual bird is 9-3 = 6 m/s

Seen from underwater, the virtual bird appears further away than actual bird by a factor n'/n = 4/3.

So actual velocity is 6 / (4/3) = 6 x 3/4 = 4.5 m/s

ujjwal · Answer

yes, since it is viewed from denser to rarer medium @experimentX

ujjwal · Answer

Thanks @Vincent-Lyon.Fr and @experimentX