Transferring Heat Energy by Radiation

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  • 0:03 Transferring Heat Energy
  • 0:50 Heat Transfer by Radiation
  • 2:22 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

After completing this lesson, you'll be able to explain how heat transfer by radiation works, and why it is important for life on Earth. You'll also learn how radiation is produced.

Transferring Heat Energy

Heat (or thermal) energy is energy in the form of the vibration and motion of the molecules in a substance. The faster those molecules vibrate and move, the more heat energy they contain.

But, of course, we all know what heat is. We feel it everyday. When we move our hands near an open fire, we feel the heat radiating from it. When we cuddle up with a loved one, we feel the heat they radiate. The thermal motion of their particles spreads into your body. But there are different ways for that heat to transfer: it can transfer by conduction, convection, or radiation.

Conduction is the transferring of heat by direct contact. Convection is transferring heat through the motions of fluids (gases and liquids). But today, we're going to talk in more detail about the third kind of heat transfer: radiation.

Heat Transfer by Radiation

Radiation is the transfer of energy through electromagnetic waves. Electromagnetic waves include things like light, infrared, ultraviolet, radio waves, microwaves, and gamma rays.

When it comes to heat transfer, the most common kind of radiation we experience in our everyday lives is infrared radiation. All warm objects produce infrared radiation: your body is producing it right now and so does a campfire. If you put your hand above a campfire, it feels even warmer because of the effects of convection, which is hot gases rising. But the reason it feels warm in front of a campfire at all is because of radiation. The only way an object wouldn't produce radiation is if it was cooled down all the way to absolute zero: that's negative 273 degrees Celsius!

Radiation is produced when the vibrations of the object's molecules cause the electrons inside them to get jiggled up and energized. If the electrons receive enough energy they'll jump up into higher orbits. But not for long - eventually they'll drop back down and produce infrared radiation. That infrared radiation travels towards you, and gives its energy to the molecules in your body, warming you up.

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