A ship sends out a 1200 Hz sound wave, which has a wavelength of 1.2 m in the water. It reflects off the ocean floor and returns to the ship in a total time of 5 seconds. How deep is the ocean at this location?

speed =frequency ×wavelength

1200×1.2=1440m/s

s=2d/t

1440=2d/5

2d=7200

d=3600m

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.

there are no contact forces mentioned on the list of choices that you've provided.