Radiant energy is a type of thermal energy transfer involving electromagnetic waves. In the case of visible light, radiant energy is visible to the human eye. However, in all other cases, it is not visible to the human eye.
Radiation is energy transmitted through electromagnetic waves or what we sometimes call radiant energy so you know what waves are, you've seen the ocean waves and you've seen a wave and if I take a rope and I move it up and down, I can make waves and those waves can have certain wavelengths, the distance from each wave okay. And it also has a frequency, how many wavelengths per unit time so if I have a wavelength and I'm moving my rope up and down really slow I'm going to have really long wavelengths and those are going to be things on this side of the electromagnetic spectrum of the radiation things like radio waves. Television waves are actually a form of radio wave or others getting smaller are micro waves, and getting a little bit smaller the wavelengths we have things like infrared waves which you feel as heat and then we we're in here the visible, visible light spectrum that's a form of electromagnetic radiation. Then we get on the far end of, of the visible light spectrum we get over to the UV rays and then we go further and we have x-rays and then when you think of radiation you might think about nuclear radiation well that's actually a form of gamma waves down here and then way the cosmic rays produced by stars in far off galaxy its with really short wave length and real large frequencies.
So the interesting thing about wavelength is, these longer wavelength tend to be very weak waves and as we move those waves gets stronger so we can learn a lot about stars for example based on what type of wavelengths they produce. If we have a star that's a red giant, it's producing red waves that's over here on the longer wavelength side of the visible light spectrum and we know that that's strong that star is a weaker star producing less energy. If we have a star that's really bright in sort of bright bluish white, we know that that star is producing a lot of energy because it's producing the stronger form of the energy on the visible light spectrum so as we go from longer wavelength to shorter wavelength we go from weaker electromagnetic radiation to stronger electromagnetic radiation and converse is we go from smaller frequency to, to larger frequency we go from weaker to stronger waves and those are some of the types of electromagnetic radiation or how energy can be transferred especially through space.