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Related Concept Videos

Emission Spectra02:39

Emission Spectra

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When solids, liquids, or condensed gases are heated sufficiently, they radiate some of the excess energy as light. Photons produced in this manner have a range of energies, and thereby produce a continuous spectrum in which an unbroken series of wavelengths is present.
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Dual Nature of Electromagnetic (EM) Radiation01:10

Dual Nature of Electromagnetic (EM) Radiation

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Electromagnetic (EM) radiation consists of electric and magnetic field components oscillating in planes perpendicular to each other and mutually perpendicular to radiation propagation through space. EM radiation can be classified as a wave, characterized by the properties of waves such as wavelength (denoted as λ) and frequency (represented by ν).
Wavelength is the distance between two consecutive peaks (the highest point) or troughs (the lowest point) in the wave. Frequency is the...
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Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
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Photoelectric Effect02:26

Photoelectric Effect

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When light of a particular wavelength strikes a metal surface, electrons are emitted. This is called the photoelectric effect. The minimum frequency of light that can cause such emission of electrons is called the threshold frequency, which is specific to the metal. Light with a frequency lower than the threshold frequency, even if it is of high intensity, cannot initiate the emission of electrons. However, when the frequency is higher than the threshold value, the number of electrons ejected...
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Fermi Level01:18

Fermi Level

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The Fermi-Dirac function is represented by an S-shaped curve indicating the probability of an energy state being occupied by an electron at a given temperature. The Fermi level is the energy level at which there is a fifty percent chance of finding an electron, and it is positioned between the lower-energy valence band and the higher-energy conduction band.
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The Bohr Model

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Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded by lighter and even tinier electrons continually moving about the nucleus was well established. This picture was called the planetary model since it pictured the atom as a miniature “solar system” with the electrons orbiting the nucleus like planets orbiting the sun. The simplest atom is hydrogen, consisting of a single proton as...
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Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry
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Non-Planck thermal emission from two-level media.

Igor A Nechepurenko, Denis G Baranov

    Optics Letters
    |July 30, 2021
    PubMed
    Summary

    Thermal emission from materials can change with temperature, deviating from typical predictions. This study explores non-Planckian thermal emission in two-level systems, impacting thermal energy harvesting and vision technologies.

    Area of Science:

    • Physics
    • Thermodynamics
    • Optics

    Background:

    • Thermal emission is a universal phenomenon, typically increasing monotonically with temperature.
    • This behavior is usually explained by Bose-Einstein statistics of the thermal photonic field.
    • However, the influence of temperature on a material's emissivity is often overlooked.

    Purpose of the Study:

    • To theoretically investigate thermal emission from structures with two-level media.
    • To explore how temperature affects thermal emission in various geometries.
    • To establish general dependencies for thermal emission evolution in these systems.

    Main Methods:

    • Theoretical analysis of thermal emission.
    • Modeling of structures incorporating two-level media.

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  • Investigation across different geometries like thin films and nanoparticles.

    • Main Results:

    • Thermal emission is non-Planckian in these systems.
    • A universal asymptotic behavior is observed at high temperatures.
    • Emissivity is shown to be temperature-dependent, deviating from standard models.

    Conclusions:

    • The temperature dependence of emissivity significantly alters thermal emission characteristics.
    • Findings suggest non-Planckian thermal emission is crucial for understanding specific material behaviors.
    • Results have potential applications in designing advanced thermal energy harvesting and thermal vision systems.