The joule and the kilowatt-hour are both units of energy. 15 kw · h is equivalent to how many joules? answer in units of j.

The solution for the problem is:

1 Watt = 1 Joule per second 
1 Watt*second = 1 Joule 

a Kilowatt is 1,000 Watts 
an hour is 60 seconds times 60 minutes or 3,600 seconds 
a Kilowatt * hour is 1,000 Watts in 3,600 seconds 

15 W*h = 15,000 Watt*hour = 15,000 Watt * 3,600 seconds = 54,000,000 Watt*second 

54,000,000 Watt*second = ? Joules 
54,000,000 Joules / second = 54,000,000 Watts

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.