It is actually well known that heat is simply a form of energy which transfers hotness from one point to the other. It is gets transfer from one point to another by three modes of which radiation is the one. The most common illustration for it is electromagnetic radiation. Light gets transferred in the form of electromagnetic radiation. Other examples are solar radiation, nuclear radiation etc Electromagnetic radiation is continuously emitted from all substances because of the molecular as well as atomic vibration accompanying the internal energy. The equilibrium state gives the internal energy proportional to the material temperature as well as that’s the reason we’re not aware of these radiant energy which constantly surrounds us as our body can detect only some portions of the spectrum. Our eyes can detect light as they’re very sensitive to changes in light occurring around us as well as our sensitive skin can detect heat radiation however unless these heat radiations is quite large we can’t sense it .