Radiation transfers thermal energy through?
a)waves
b)direct contact
c)particles
d) liquid movement?

A)waves

Explanation:

In radiation mode of heat transfer we do not require any medium to transfer energy from one point to other.

Here in radiation mode of heat transfer energy is being transferred by electromagnetic waves in which energy is propagated in form of electric field and magnetic field energy.

here the electromagnetic waves will travel at the speed of light and it is the fastest mode of heat transfer

so here the correct answer will be

A)waves

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.