SafekipediaRadiant energy
Adapted from Wikipedia · Discoverer experience
In physics, radiant energy refers to the energy carried by electromagnetic and gravitational radiation. It is measured in joules (J), the same unit we use for other types of energy. Scientists often use the symbol Qe to represent radiant energy, where the "e" stands for "energetic."
Radiant energy can be calculated by adding up the radiant flux, or power, over a certain period of time. This helps us understand how much energy is being transferred by waves or particles. Whether the radiation is visible light or a type we cannot see, radiant energy plays a key role in many natural and technological processes.
Terminology use and history
The term "radiant energy" is often used in fields like radiometry, solar energy, heating, and lighting. Sometimes, it is also used in other areas such as telecommunications. In modern technology, especially when moving power from one place to another, "radiant energy" can mean the electromagnetic waves themselves, not just their energy.
Radiant energy also includes gravitational radiation. For instance, the first gravitational waves ever observed came from a collision of black holes, releasing a huge amount of energy.
Analysis
Radiant energy is the energy carried by light and other types of waves. We can think of it as tiny packets of energy called photons or as waves that move through space. Both ways of looking at it help us understand how energy travels.
When these waves hit something, they can warm it up. For example, sunlight makes the ground hotter. This can happen with many kinds of waves, not just the ones we see with our eyes. Waves can also bounce off objects or spread out in different directions.
Radiant energy helps move energy into and out of things, like how solar panels use sunlight to make electricity or how the Earth gets warm from the Sun. The Sun creates this energy through a powerful process inside it.
Applications
Radiant energy is used for heating spaces. It can be created using electric infrared lamps or taken from sunlight to warm water. The heat comes from a warm surface, like a floor or wall, and warms people and objects directly, not the air. This can make a room feel comfortable even if the air is cooler than in a regular heated building.
Radiant energy has many other uses, such as checking and inspecting things, separating items, and sending messages. These uses usually need a source of radiant energy and a detector that senses the radiation and changes it into an electric signal or another noticeable form, like making photographic film show an image.
SI radiometry units
| Quantity | Unit | Dimension | |||
|---|---|---|---|---|---|
| Name | Symbol | Name | Symbol | ||
| Radiant energy | Qe | joule | J | M⋅L2⋅T−2 | |
| Radiant energy density | we | joule per cubic metre | J/m3 | M⋅L−1⋅T−2 | |
| Radiant flux | Φe | watt | W = J/s | M⋅L2⋅T−3 | |
| Spectral flux | Φe,ν | watt per hertz | W/Hz | M⋅L2⋅T −2 | |
| Φe,λ | watt per metre | W/m | M⋅L⋅T−3 | ||
| Radiant intensity | Ie,Ω | watt per steradian | W/sr | M⋅L2⋅T−3 | |
| Spectral intensity | Ie,Ω,ν | watt per steradian per hertz | W⋅sr−1⋅Hz−1 | M⋅L2⋅T−2 | |
| Ie,Ω,λ | watt per steradian per metre | W⋅sr−1⋅m−1 | M⋅L⋅T−3 | ||
| Radiance | Le,Ω | watt per steradian per square metre | W⋅sr−1⋅m−2 | M⋅T−3 | |
| Spectral radiance Specific intensity | Le,Ω,ν | watt per steradian per square metre per hertz | W⋅sr−1⋅m−2⋅Hz−1 | M⋅T−2 | |
| Le,Ω,λ | watt per steradian per square metre, per metre | W⋅sr−1⋅m−3 | M⋅L−1⋅T−3 | ||
| Irradiance Flux density | Ee | watt per square metre | W/m2 | M⋅T−3 | |
| Spectral irradiance Spectral flux density | Ee,ν | watt per square metre per hertz | W⋅m−2⋅Hz−1 | M⋅T−2 | |
| Ee,λ | watt per square metre, per metre | W/m3 | M⋅L−1⋅T−3 | ||
| Radiosity | Je | watt per square metre | W/m2 | M⋅T−3 | |
| Spectral radiosity | Je,ν | watt per square metre per hertz | W⋅m−2⋅Hz−1 | M⋅T−2 | |
| Je,λ | watt per square metre, per metre | W/m3 | M⋅L−1⋅T−3 | ||
| Radiant exitance | Me | watt per square metre | W/m2 | M⋅T−3 | |
| Spectral exitance | Me,ν | watt per square metre per hertz | W⋅m−2⋅Hz−1 | M⋅T−2 | |
| Me,λ | watt per square metre, per metre | W/m3 | M⋅L−1⋅T−3 | ||
| Radiant exposure | He | joule per square metre | J/m2 | M⋅T−2 | |
| Spectral exposure | He,ν | joule per square metre per hertz | J⋅m−2⋅Hz−1 | M⋅T−1 | |
| He,λ | joule per square metre, per metre | J/m3 | M⋅L−1⋅T−2 | ||
| See also: | |||||
Related articles
This article is a child-friendly adaptation of the Wikipedia article on Radiant energy, available under CC BY-SA 4.0.
Images from Wikimedia Commons. Tap any image to view credits and license.