You’ve already learned how conduction moves heat between objects that are touching and convection moves heat by mixing up liquids and gases. But how does heat from the sun warm up you skin while you are playing at the pool? This animation will shine a light – literally – on the final method for transferring thermal energy.
Watch this video to learn about how electromagnetic waves--also known as light--transfers thermal energy. As you watch the segment, you might want to check the definitions of specific terms. In addition to the glossary words highlighted above, thermal radiation will be described.
Stop the animation at any time, watch it again, or read the transcript.
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Thermal energy is all about moving molecules. When molecules move, they bump and ping off of each other to transfer their energy. While they do this, they are also creating electromagnetic waves, which transfer energy outward. This transfer of heat via electromagnetic waves is called thermal radiation.
Everything-- all matter-- emits some level of thermal radiation. It is the reason a campfire glows, how microwaves heat things up, and why you show up on a thermal camera. Matter, which is hot, emits more and matter which is cold emits less. And when things are really charged up, you can feel part of the radiation as heat, but you can also see part of that radiation as visible light (ie. campfire, hot glowing poker). But all of this is the transfer of thermal energy via electromagnetic waves.
And most importantly for us here on Earth-- electromagnetic waves can travel even when there are no particles present, for instance, in the vacuum of space. They are the reason the sun's heat gets from there to here.
So go ahead and let the sunshine (aka thermal radiation) in.
In the space below give two examples of heat transfer by thermal radiation. For each example, be sure to describe what is happening to the motion of the molecules.