If you’ve had a particularly good hair day, you might’ve heard someone describe you as looking radiant. But radiant energy is more than just a way to describe someone’s glow; it’s an important part of physics, and a way in which we understand our universe.
If you’ve never heard of radiant energy in this context, don’t worry — we’ve got you covered. Here’s your complete guide to radiant energy.
What Is the Definition of Radiant Energy?
Radiant energy is the energy transferred by electromagnetic or gravitational radiation. If that sounds complicated, it’s easier to understand if we take it piece by piece.
Most of the time when the term radiant energy is used, it’s to describe energy transferred by electromagnetic radiation, most often by particles called photons. Of the fundamental forces of the universe, electromagnetism describes energy that’s transferred by waves through space at the speed of light. That energy, transferred by electromagnetic radiation through waves, is called radiant energy.
Radiant energy is also used to describe the energy transferred by gravitational radiation. When we observe gravitational waves moving through space, the energy they carry is radiant energy.
How Is Radiant Energy Measured?
Radiant energy is measured in joules, sometimes abbreviated as J. This unit measures the energy of electromagnetic radiation emissions, which is also known as radiant energy.
How Does Radiant Energy Work?
Radiant energy works along wavelengths. These waves work the same as the ones we might see at the beach: They have peaks and valleys, they move more or less in a regular pattern, and they transfer energy as they move.
In the case of electromagnetic radiation, the energy being transferred through photons that travel these waves is radiant energy.
To better understand how radiant energy works, we should define three terms used to describe these waves:
Amplitude describes the height of a wave, taken by measuring from the peak all the way down to the trough of the wave.
Wavelength describes how long the repeated portion of a wave is. This is taken by measuring the distance from one peak of the wave to the next peak of the wave.
Frequency describes how often the wave repeats its pattern in a given period. The frequency of a wave is inversely proportional to its wavelength — the longer the wavelength, the less often it repeats in a given period, and therefore the lower its frequency. Conversely a wave with a short wavelength will repeat more often, and therefore have a higher frequency.
Waves with higher frequencies carry with them more energy. This means that electromagnetic radiation with higher frequencies transfers more radiant energy.
What Are the 7 Types of Radiant Energy?
Radiant energy is transferred through the emission of electromagnetic radiation, and there are seven different forms across the electromagnetic spectrum. Here they are, ordered from lowest frequency to highest:
Radio Waves
You’re probably familiar with radio waves, as these are what we use when we adjust the dial in our car to find that perfect tune. Radio waves have the longest wavelengths of any wave in the electromagnetic spectrum, and the lowest frequencies, as well.
Microwaves
Unsurprisingly, the radiant energy of microwaves are used to heat up food in microwave ovens. But these relatively large wavelength (and low frequency) electromagnetic waves are also used in radar applications.
Infrared Radiation
Infrared radiation, sometimes abbreviated as IR, has a shorter wavelength and higher frequency than both radio waves and microwaves. Infrared radiation isn’t visible to the human eye, but with special cameras we can see this type of electromagnetic radiation and the radiant energy it transmits.
These special cameras can be used to see sources of heat (thermal cameras) or to see objects in low visible light conditions (night vision goggles).
Visible Light
The visible light we need to see is, in fact, a form of electromagnetic radiation emissions. This also means that our sight is dependent on photons and the radiant energy they carry.
Our sun is the source of most of the visible light on earth. In fact, the sun emits radiant energy along every wavelength (and frequency) of the electromagnetic spectrum.
This is why you can’t stare at the sun for long — the visible light it emits carries with it too much radiant energy for our eyes to handle!
Ultraviolet Radiation
Ultraviolet radiation, sometimes abbreviated as UV, is on the higher frequency side of the electromagnetic spectrum. Ultraviolet radiation carries with it plenty of radiant energy, so much so that it can actually be dangerous to our health if precautions aren’t taken.
Ultraviolet radiation has a number of uses, from surface sterilization to tanning beds, but in each of these use cases, its radiant energy needs to be carefully controlled so as not to hurt our health.
X-Rays
X-rays have very small wavelengths and extremely high frequencies. This form of electromagnetic radiation carries with it an enormous quantity of radiant energy, and like UV radiation, it can be harmful to our health if we’re not careful with it.
X-rays are used in radiology, which allows us to see inside the human body in ways that would otherwise be unknown to us. The next time you’re going through airport security, you’ll know that radiant energy is being used to help in the screening process.
Gamma Rays
Gamma rays exist at the very top end of the electromagnetic spectrum, which means they have the shortest wavelengths and largest frequencies of any form of electromagnetic radiation. This also means they carry the largest amounts of radiant energy.
Gamma rays are extremely damaging to biological life, and as such they’re extremely dangerous to human health. Thankfully the sources of this kind of electromagnetic radiation are relatively rare.
What Is the Source of Radiant Energy?
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Radiant energy can come from a wide variety of sources. Radiant energy transferred through gravitational radiation can come from the gravitational force of stars, planets, or even black holes.
The sources of radiant energy that is transmitted through electromagnetic radiation can also come from stars, and here on earth, our sun is the major source of radiant energy.
Does Radiant Energy Come From the Sun?
Yes, radiant energy comes from the sun. The sun emits electromagnetic radiation — also known as solar radiation — in every range of the electromagnetic spectrum, and this radiation contains within it radiant energy.
What Are Examples of Radiant Energy?
Perhaps the most common example of radiant energy is something we see all around us: visible light. In fact, without the radiant energy present in visible light, we wouldn’t be able to see at all.
Other examples of radiant energy include microwaves, the warmth we enjoy sitting around a campfire, and even the ability to develop a suntan by sitting out in sunlight.
How Is Radiant Energy Used?
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Radiant energy has a wide variety of uses, and in fact is critical to biological life and our modern civilization.
Radiant energy is used by plants in the process of photosynthesis: plants are able to convert the radiant energy of our sun into chemical energy that they can use to grow. Animals and humans then are able to use that chemical energy as these plants are consumed. In this way, radiant energy is a cornerstone of the food chain, and is necessary for our sustenance.
Lately, humans have begun harnessing radiant energy to produce electricity through solar power. Solar energy is a renewable energy resource that converts the radiant energy of the sun into electric power. We can then use this solar power for a variety of applications.
The uses of radiant energy don’t end there, though. We use radiant energy every time we heat something up in the microwave, by using microwave electromagnetic radiation. Some surface disinfectant systems use the radiant energy present in ultraviolet radiation to eliminate bacteria and sanitize surfaces.
Is Radiant Energy Renewable?
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Yes, you could consider radiant energy to be renewable. Most of the time when we refer to radiant energy here on earth, we refer to energy sourced from the sun.
The sun’s life cycle isn’t infinite, but it is long enough to consider the sun’s energy — and in this case its radiant energy — a renewable resource. That’s good news for us!
What Is the Meaning of Radiant Heat?
Radiant heat is a form of radiant energy that has specific applications for keeping things warm. Radiant heat is actually a form of electromagnetic radiation — more specifically, it’s a form of infrared radiation.
What Makes Radiant Heat?
Exothermic chemical reactions make radiant heat. Put another way, radiant heat occurs when the heat emanating from a heat source is allowed to move through a space.
The heat from a fireplace heats up a room through radiant heat: The increased temperature of the fire in the fireplace sends waves of radiant heat in the form of infrared radiation throughout the room, raising the overall temperature.
Does Radiant Heat Warm the Air?
Yes, radiant heat can warm the air, and in fact this is the primary use of radiant heat. We use this often in our own homes, whether we know it as radiant heat or not.
As we already mentioned, fireplaces are textbook examples of radiant heat sources in our homes. So too are aptly named radiators, which use hot water to heat up metal, which then heats up the air around it through the transfer of radiant heat.
If we’re able to control these sources of radiant heat carefully, we can manage the air temperature of our homes to be more comfortable, even in the dead of winter.
Radiant Energy Is All Around Us
Radiant energy is a fixture of our universe, and while some parts of it are visible to our eyes, there’s plenty of it moving around that we can’t see.
Radiant energy comes in seven different forms, all categorized by frequency and wavelength. Each form of this electromagnetic radiation has different uses — and in some cases, dangers.
If this article made you curious about energy in our universe, you can learn a lot more about energy-related topics on the Tara Energy blog.
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