What is Radiant Energy? - Definition & Examples

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  • 0:05 What is Radiant Energy?
  • 1:58 How Does Radiant Energy Work?
  • 3:06 Electromagnetic Waves
  • 4:26 What Do Waves Have to…
  • 5:15 Application of Radiant Energy
  • 6:27 Lesson Summary
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Lesson Transcript
Instructor: John Simmons

John has taught college science courses face-to-face and online since 1994 and has a doctorate in physiology.

This lesson defines and describes radiant energy in its different forms. The different types of electromagnetic waves created by radiant energy are identified and described as well. This includes X-rays, microwaves, and radio waves, to mention a few.

What Is Radiant Energy?

Have you ever wondered what the temperature is in outer space? No matter how you express it, it is very cold, even close to the sun. We can explain this phenomenon in terms of energy, which is the ability to do work, and matter, which is anything that has mass and takes up space. Energy does work when it forces something to move. As the particles move faster, the temperature increases. Well, if there's nothing there to move, no work can be done, even if energy is available.

You see, outer space is void of matter. Therefore, the energy from the sun doesn't have anything to warm up. We feel the warmth of the sun as the sun's energy forces our bodies' molecules to move faster - in other words, work harder. Let's explore this concept in more detail.

The energy from the sun is called radiant energy, or energy possessed by vibrating particles. Vibrating particles in the sun create waves that travel through space and time. We call these waves created by vibrating particles electromagnetic waves. Electromagnetic waves contain both electrical and magnetic properties that allow them to travel through space, even though space is void of matter. Other waves, for example, the waves in the ocean, require matter to move.

We can easily demonstrate the formation of waves from vibrating particles. Here - let's do a little experiment. If you've got a cup of coffee, assuming it's cool enough, or a glass of water by you, just stick your finger down in the water and wiggle it - vibrate it - back and forth, and watch the waves form. Now, while these are not electromagnetic waves, the concept is similar to how vibration forms.

How Does Radiant Energy Work?

When the waves touch our skin, the skin molecules move faster and warm us up.
Waves Excite Skin Molecules

As we just discussed, electromagnetic waves can travel through outer space. They can travel for long distances, and they move at the speed of light. Work is done by radiant energy as the electromagnetic waves come into contact with particles and cause them to move. Let's examine the sun as a source of radiant energy.

Radiant energy from the sun is specifically referred to as solar energy. The sun contains a tremendous amount of radiant energy that produces electromagnetic waves. These waves travel away from the sun through space and time. When the waves come into contact with some object - let's say our skin - they cause the molecules in our skin to move faster. As the molecules move faster, we feel warmer.

Those same electromagnetic waves traveling through space don't do any work because there isn't anything to contact. At the same time, there is nothing to stop the waves, so they continue to travel until they hit something.

What Are Electromagnetic Waves?

To better understand how radiant energy works, we need to look at electromagnetic waves in a bit more detail. Electromagnetic waves are similar to other waves, like waves in the ocean, in that they have high parts, and they have low parts, and they move. The tops of the waves are called crests, and the bottom of the waves are called troughs. Just as there are different kinds of waves, there are different types of electromagnetic waves.

Each type of electromagnetic wave is defined by its wavelength. Well, what's that? It's simply the distance between the waves. While it is easier to measure the wavelength of waves in the ocean because we can see them, scientists have come up with ways to measure the wavelength of electromagnetic waves, even though we can't see them.

Electromagnetic waves are defined by their wavelength.
Electromagnetic Waves Defined by Wavelength

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