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  2. Thermal radiation - Wikipedia

    en.wikipedia.org/wiki/Thermal_radiation

    At any given temperature, there is a frequency f max at which the power emitted is a maximum. Wien's displacement law, and the fact that the frequency is inversely proportional to the wavelength, indicates that the peak frequency f max is proportional to the absolute temperature T of the black body. The photosphere of the sun, at a temperature ...

  3. Heat transfer physics - Wikipedia

    en.wikipedia.org/wiki/Heat_transfer_physics

    Using this plane-wave displacement, the equation of motion becomes the eigenvalue equation [15] [16] (,) = (), where M is the diagonal mass matrix and D is the harmonic dynamical matrix. Solving this eigenvalue equation gives the relation between the angular frequency ω p and the wave vector κ p , and this relation is called the phonon ...

  4. Planck's law - Wikipedia

    en.wikipedia.org/wiki/Planck's_law

    According to Planck's distribution law, the spectral energy density (energy per unit volume per unit frequency) at given temperature is given by: [4] [5] (,) = ⁡ alternatively, the law can be expressed for the spectral radiance of a body for frequency ν at absolute temperature T given as: [6] [7] [8] (,) = ⁡ where k B is the Boltzmann ...

  5. Vibrational temperature - Wikipedia

    en.wikipedia.org/wiki/Vibrational_temperature

    The vibrational temperature is commonly used in thermodynamics, to simplify certain equations.It has units of temperature and is defined as = ~ = where is the Boltzmann constant, is the speed of light, ~ is the wavenumber, and (Greek letter nu) is the characteristic frequency of the oscillator.

  6. List of equations in wave theory - Wikipedia

    en.wikipedia.org/wiki/List_of_equations_in_wave...

    The group velocity is the rate at which the wave envelope, i.e. the changes in amplitude, propagates. The wave envelope is the profile of the wave amplitudes; all transverse displacements are bound by the envelope profile.

  7. Doppler effect - Wikipedia

    en.wikipedia.org/wiki/Doppler_effect

    The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. [ 1 ] [ 2 ] [ 3 ] The Doppler effect is named after the physicist Christian Doppler , who described the phenomenon in 1842.

  8. Heat equation - Wikipedia

    en.wikipedia.org/wiki/Heat_equation

    The behavior of temperature when the sides of a 1D rod are at fixed temperatures (in this case, 0.8 and 0 with initial Gaussian distribution). The temperature approaches a linear function because that is the stable solution of the equation: wherever temperature has a nonzero second spatial derivative, the time derivative is nonzero as well.

  9. Outgoing longwave radiation - Wikipedia

    en.wikipedia.org/wiki/Outgoing_longwave_radiation

    The greenhouse effect is visible as the area of the upper red area, and the greenhouse effect associated with CO 2 is directly visible as the large dip near the center of the OLR spectrum. [ 26 ] The reduction of the outgoing longwave radiation (OLR), relative to longwave radiation emitted by the surface, is at the heart of the greenhouse effect .