1. a sonar pulse is sent to the ocean bottom which is 25◦ celsius. it takes 4.2 seconds for the wave echo to return to the ship. how deep is the ocean bottom? medium m/s air 0○c 331 air 20○c 343 helium 0○c 972 water 25○c 1,493 seawater 25○c 1,533 copper 25○c 3,560 iron 25○c 5,130

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.