Is light radiation always accompanied by thermal or heat radiation ?
Radiation is a general term for electromagnetic waves (the same “stuff” as light)…either that or radioactive decay products. Is light radiation always accompanied by infrared radiation” (infrared is what you really mean by “thermal radiation” or “heat radiation”) Well, when produced by a black body (or even a gray body), yes. Black bodies radiate a continuous spectrum as per a theoretical intensity of frequency distribution based on temperature. All objects not cold enough to freeze your hand off, and not being theoretical white bodies will emit infrared radiation…some more than others. Although, the method of production of light in theory doesn’t have to also produce infrared. Monochromatic light sources do exist (operate without depending on black body radiation), and if you chill a monochromatic light source such that its temperature is ridiculously low (or make its surface extremely reflective in the infrared spectrum), it can emit visible light without emitting infrared.
