Heat radiation is all around us. Some common examples are microwaves, the sun, lamps, and fireplaces!
If not for heat radiation, humans would have died from the cold long ago. When we make a fire and the heat is warming our skin, it is actually the heat radiating to our skin.
Learn more about radiant heat transfer by reading on! It is one of the fundamental discoveries of modern science.
Energy transfer as an idea has not been around for long.
We used to have theories like the “phlogiston theory”, proposed in 1667. We also have the ideas from antiquity: if you have ever encountered Aristotle’s writings, you may recall that he wrote about the four elements of “moist” “dry” “hot” and “cold”.
Of course, these theories have since been debunked,
Humans could certainly sense temperature from long ago, but they did not know about energy transfer until much later, about 200 years before modern-day.
Breaking Down Radiant Heat Transfer
When we talk about radiant heat transfer, we are actually talking about something called “electromagnetic radiation” or electromagnetic waves.
It actually includes visible light in the spectrum, alongside radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
Even though the sun is tens of millions of light-years away from us, it emits so much electromagnetic radiation that we can both feel its heat, and see its visible light. Heat and light are both parts of the EMR spectrum. Just like you might feel the heat from a thermal blanket, you can feel the heat from the sun.
The principle of radiation is the same in both cases.
Infrared radiation is especially good at carrying heat, but you cannot see it. If you could, then you would see that warm objects emit a certain glow.
When you have a hot object, the energy waves are constantly “radiating” out from it and being absorbed or reflected off of other things in the proximity. The energy bounces off or is absorbed by windows, walls, your skin, and much more!
In Greater Detail
Note that radiation is different from conduction and convection in terms of energy transport.
Conduction involves objects that are in direct contact with each other. When your hand touches a hot stove, heat is transferred through the fast-moving particles bumping into the slower particles in your hand.
Convection involves the flow of fluids. Have you ever heard that hot air rises, and cold air sinks? This involves the movement of gases in your environment. Similarly, convection occurs when solid objects encounter gaseous objects.
When fan blades rotate in the air, they push the gas molecules of air away, cooling down the area.
Radiation is different because it does not involve molecules bumping into each other. A small particle of energy is transferred between molecules, or emitted from one molecule and then absorbed by some other molecule in the vicinity.
Thermal Radiation Explained
Now you know how heat radiant heat transfer works! You can find out more about the meaning of many other scientific concepts in our news and education sections.