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  2. Impedance of free space - Wikipedia

    en.wikipedia.org/wiki/Impedance_of_free_space

    The impedance of free space (that is, the wave impedance of a plane wave in free space) is equal to the product of the vacuum permeability μ 0 and the speed of light in vacuum c 0. Before 2019, the values of both these constants were taken to be exact (they were given in the definitions of the ampere and the metre respectively), and the value ...

  3. Free-space path loss - Wikipedia

    en.wikipedia.org/wiki/Free-space_path_loss

    In telecommunications, the free-space path loss (FSPL) (also known as free-space loss, FSL) is the attenuation of radio energy between the feedpoints of two antennas that results from the combination of the receiving antenna's capture area plus the obstacle-free, line-of-sight (LoS) path through free space (usually air). [1]

  4. Vacuum permittivity - Wikipedia

    en.wikipedia.org/wiki/Vacuum_permittivity

    e 2 ⋅eV −1 ⋅μm −1 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.

  5. Wave impedance - Wikipedia

    en.wikipedia.org/wiki/Wave_impedance

    In free space the wave impedance of plane waves is: = (where ε 0 is the permittivity constant in free space and μ 0 is the permeability constant in free space). Now, since = = (by definition of the metre),

  6. Space charge - Wikipedia

    en.wikipedia.org/wiki/Space_charge

    As an application example, the steady-state space-charge-limited current across a piece of intrinsic silicon with a charge-carrier mobility of 1500 cm 2 /V-s, a relative dielectric constant of 11.9, an area of 10 −8 cm 2 and a thickness of 10 −4 cm can be calculated by an online calculator to be 126.4 μA at 3 V. Note that in order for this ...

  7. Hilbert space - Wikipedia

    en.wikipedia.org/wiki/Hilbert_space

    Let L 2 (X, μ) be the space of those complex-valued measurable functions on X for which the Lebesgue integral of the square of the absolute value of the function is finite, i.e., for a function f in L 2 (X, μ), | | <, and where functions are identified if and only if they differ only on a set of measure zero.

  8. Critical frequency - Wikipedia

    en.wikipedia.org/wiki/Critical_frequency

    Critical frequency is the highest magnitude of frequency above which the waves penetrate the ionosphere and below which the waves are reflected back from the ionosphere. It is denoted by "f c". Its value is not fixed and it depends upon the electron density of the ionosphere.

  9. Minkowski space - Wikipedia

    en.wikipedia.org/wiki/Minkowski_space

    Where v is velocity, x, y, and z are Cartesian coordinates in 3-dimensional space, c is the constant representing the universal speed limit, and t is time, the four-dimensional vector v = (ct, x, y, z) = (ct, r) is classified according to the sign of c 2 t 2 − r 2. A vector is timelike if c 2 t 2 > r 2, spacelike if c 2 t 2 < r 2, and null or ...