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  2. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    The speed of light in vacuum is usually denoted by a lowercase c, for "constant" or the Latin celeritas (meaning 'swiftness, celerity'). In 1856, Wilhelm Eduard Weber and Rudolf Kohlrausch had used c for a different constant that was later shown to equal √ 2 times the speed of light in vacuum.

  3. Photon energy - Wikipedia

    en.wikipedia.org/wiki/Photon_energy

    c is the speed of light in vacuum h is the Planck constant The photon energy at 1 Hz is equal to 6.626 070 15 × 10 −34 J , which is equal to 4.135 667 697 × 10 −15 eV .

  4. Vacuum energy - Wikipedia

    en.wikipedia.org/wiki/Vacuum_energy

    The field strength of vacuum energy is a concept proposed in a theoretical study that explores the nature of the vacuum and its relationship to gravitational interactions. The study derived a mathematical framework that uses the field strength of vacuum energy as an indicator of the bulk (spacetime) resistance to localized curvature.

  5. Zero-point energy - Wikipedia

    en.wikipedia.org/wiki/Zero-point_energy

    A vacuum can be viewed not as empty space but as the combination of all zero-point fields. In quantum field theory this combination of fields is called the vacuum state, its associated zero-point energy is called the vacuum energy and the average energy value is called the vacuum expectation value (VEV) also called its condensate.

  6. Electromagnetic wave equation - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_wave_equation

    is the speed of light (i.e. phase velocity) in a medium with permeability μ, and permittivity ε, and ∇ 2 is the Laplace operator. In a vacuum, v ph = c 0 = 299 792 458 m/s, a fundamental physical constant. [1] The electromagnetic wave equation derives from Maxwell's equations.

  7. Refractive index - Wikipedia

    en.wikipedia.org/wiki/Refractive_index

    The absolute refractive index n of an optical medium is defined as the ratio of the speed of light in vacuum, c = 299 792 458 m/s, and the phase velocity v of light in the medium, =. Since c is constant, n is inversely proportional to v : n ∝ 1 v . {\displaystyle n\propto {\frac {1}{v}}.}

  8. Vacuum permittivity - Wikipedia

    en.wikipedia.org/wiki/Vacuum_permittivity

    Vacuum permittivity, commonly denoted ε 0 (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space , the electric constant , or the distributed capacitance of the vacuum.

  9. Radiation pressure - Wikipedia

    en.wikipedia.org/wiki/Radiation_pressure

    The magnitude, denoted by S, divided by the speed of light is the density of the linear momentum per unit area (pressure) of the electromagnetic field. So, dimensionally, the Poynting vector is S = ⁠ power / area ⁠ = ⁠ rate of doing work / area ⁠ = ⁠ ⁠ ΔF / Δt ⁠ Δx / area ⁠, which is the speed of light, c = Δx / Δt, times ...