A bird is flying 3m above the surface of water. If the bird is diving vertically down with speed 6 m/s, then his apparent velocity as seen by a stationary fish underwater is?
the fish is under water…so if the real height of bitd is h m above the surface the fish will see it at h’such thatreal height/apparent height = refractive index of water =3/4 = g(mu)ah/ h’ = 3/4 so the speed dh/dt / dh’/dt = 3/4 ,v(bird)/ v’(as seen by fish) = 3/4so the velocityseen by fish =dh’/dt = (4/3 ) * dh/dt= (4/3 )* 6 m/s = 8 m/s
A person in a boat sees a fish in the water (n=1.33) at an angle of 40 degrees relative to the waters surface?
Angle of incidence (to vertical) for the 'seen' position .. i = 90 - 40 = 50º True angle = angle of refraction (r) to vert. = (90 - r) to horizontal sin r = sin i / n = sin 50 / 1.33 .. sin r = 0.5760 .. .. r = 35.20º True angle to horiz. = (90 - 35.20) .. .. ►54.80º