Thermal Radiation: What is Nonthermal Radiation?

In summary, thermal radiation refers to radiation from an ensemble of quantum states that is described by a Boltzman distribution, which has nothing to do with heat. Blackbody radiation is a type of thermal radiation, while nonthermal radiation encompasses all other types of radiation. This includes light from filament light bulbs, LCD monitors, and the sun, which are thermal, as well as light reflected, diffracted, or partly transmitted by bodies, which is nonthermal. Additionally, the emission of photons by atoms when they jump into lower states is considered thermal radiation due to the statistical behavior of the quantum states, not because of heat.
  • #1
Lapidus
344
11
I read somewhere on the net that almost 100 percent of radiation in the universe is thermal.

What then is nonthermal radiation? Can it be said that blackbody radiation is purely thermal?

What about all the radiation that is reflected, diffracted or partly transmitted by bodies, is that nonthermal radiation?

I also read that emission of photon by atoms when they jump into lower states is thermal radiation. How can this be? That has nothing to do with heat.

thanks
 
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  • #2
Lapidus said:
I read somewhere on the net that almost 100 percent of radiation in the universe is thermal.

What then is nonthermal radiation? Can it be said that blackbody radiation is purely thermal?

What about all the radiation that is reflected, diffracted or partly transmitted by bodies, is that nonthermal radiation?

I also read that emission of photon by atoms when they jump into lower states is thermal radiation. How can this be? That has nothing to do with heat.

thanks

Rigorously speaking, "thermal radiation" should be taken to mean, "Radiation from an ensemble of quantum states that is described by a Boltzman distribution" (see http://en.wikipedia.org/wiki/Boltzmann_distribution). It has *nothing* to do with heat per se, but instead only has to do with the statistical behavior of quantum systems defined by a given temperature. The frequencies of the radiation will depend on the spacing between the quantum states. The temperature will determine the relative populations of the quantum states, which are assumed to be in thermal equilibrium.
 
  • #3
Thermal radiation is black body radiation. Nonthermal radiation is anything else. Light from a filament light bulb is thermal, while light from your LCD monitor is nonthermal. Light from the sun is themal (mostly), while light from aurora borealis is not. Light reflected by an opaque object loses its thermal nature since some wavelengths are reflected more strongly than others.
 
  • #4
Lapidus said:
I read somewhere on the net that almost 100 percent of radiation in the universe is thermal.

What then is nonthermal radiation? Can it be said that blackbody radiation is purely thermal?

What about all the radiation that is reflected, diffracted or partly transmitted by bodies, is that nonthermal radiation?

I also read that emission of photon by atoms when they jump into lower states is thermal radiation. How can this be? That has nothing to do with heat.

thanks

Please cite ALL sources. https://www.physicsforums.com/blog.php?b=2703" [Broken].

Zz.
 
Last edited by a moderator:
  • #5


Nonthermal radiation refers to any type of electromagnetic radiation that is not caused by thermal energy. This includes radiation from sources such as radio waves, microwaves, and X-rays, which are generated by processes other than heating. This type of radiation can be found throughout the universe, from natural sources such as stars and galaxies to man-made sources such as cell phones and microwave ovens.

While it is true that a large portion of the radiation in the universe is thermal, it is not the only type of radiation present. Nonthermal radiation plays a crucial role in many physical processes, such as communication and medical imaging.

Blackbody radiation, which is the electromagnetic radiation emitted by a perfect thermal radiator, is primarily thermal in nature. However, it can also contain nonthermal components, such as radiation from electronic transitions in atoms.

Radiation that is reflected, diffracted, or transmitted by bodies can also contain both thermal and nonthermal components. For example, sunlight contains both thermal radiation from the Sun's surface and nonthermal radiation from processes such as nuclear fusion.

The emission of photons by atoms when they jump into lower energy states is a form of thermal radiation, as it is caused by the thermal energy of the atom. This process, known as spontaneous emission, is a fundamental aspect of quantum mechanics and is not related to the concept of heat in the classical sense.

In summary, nonthermal radiation is any type of electromagnetic radiation that is not caused by thermal energy. It can be found throughout the universe and plays an important role in many physical processes. While thermal radiation is the primary type of radiation in the universe, nonthermal radiation should not be overlooked or underestimated in its significance.
 

1. What is thermal radiation?

Thermal radiation is a type of electromagnetic radiation that is emitted by an object as a result of its temperature. It is a form of heat transfer that occurs when an object's temperature is higher than its surroundings.

2. What is nonthermal radiation?

Nonthermal radiation is a type of electromagnetic radiation that is not a result of the temperature of an object. It can be produced by a variety of sources, including atoms, molecules, and subatomic particles.

3. How is thermal radiation different from nonthermal radiation?

Thermal radiation is emitted by an object due to its temperature, while nonthermal radiation is produced by other sources. Thermal radiation is typically in the infrared region of the electromagnetic spectrum, while nonthermal radiation can be found in a wide range of frequencies.

4. What are some examples of nonthermal radiation?

Some examples of nonthermal radiation include radio waves, microwaves, X-rays, and gamma rays. These types of radiation are produced by various natural and man-made sources, such as stars, nuclear reactions, and electronic devices.

5. How is nonthermal radiation used in everyday life?

Nonthermal radiation is used in a variety of ways in everyday life. For example, radio waves are used for communication and radar systems, microwaves are used for cooking food, and X-rays are used in medical imaging. Additionally, nonthermal radiation is used in scientific research, such as in astronomy and particle physics.

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