In my uni notes my lecturer wrote that energy is either transferred as HEAT or WORK. (he said "all other modes of energy transfer other than heat are called work". Heat can obviously be transferred by convection, conduction or radiation. In many places it says that heat radiation is 'infrared radiation'. This makes sense as infrared is the type of radiation that makes us feel the warmest (although other electromagnetic radiations such as light and microwaves can also make us feel warm... but perhaps this is just due to a bit of infrared radiation being mixed in with them?) So, what I want to know is, are all the forms of electromagnetic radiation (such as x-rays, light, radio waves and microwaves) in addition to infrared classified as 'heat transfer of energy'?
I have 2 hypotheses...
- Perhaps my lecturer got it wrong... energy can be transmitted/transferred by heat, work OR radiation
- All types/wavelengths of electromagnetic radiation ARE in fact heat, but our bodies sense the infrared as heat/warmth more so than the other types, as it hits the outside of our bodies where there are heat sensors. For example, if we stand near lots of microwaves, we may not initially sense the thermal energy as 'heat' as it is heating up water inside our bodies rather than the heat sensors in the skin. However, our body would gradually heat up and we would start to feel the thermal energy we had acquired as heat. And another example, we can get sunburnt from UV rays even without feeling too hot (ie the burn can be out of proportion to the feeling of heat). This may be because the heat and therefore thermal energy we get from UV rays also doesn't interact with heat sensors in the skin as well as infrared can. So it is more of a 'human sense' issue on how well we can 'sense' heat rather than whether heat is actually transferred or not.
Are either of my hypotheses correct? Or is there another explanation? Thank you!