Question

can anyone tell me what the source of electromagnetic radiation in the sun is?

Answer 1

Well, that would be hydrogen fusion. That is where all the energy comes from. The different wavelengths we get are a result of many other physical processes happening. One interesting thing to note is that the Sun is the colour it is because it is almost like a black body (a perfect emitter of radiation). The temperature of the surface can be used to calculate the peak wavelength of light given off using Wiens displacement law: http://hyperphysics.phy-astr.gsu.edu/hbase/wien.html. The Suns blackbody temperature is roughly 5770 Kelvin.