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  2. Wave equation - Wikipedia

    en.wikipedia.org/wiki/Wave_equation

    This means that the value of v is constant on characteristic lines of the form x + ct = x 0, and thus that v must depend only on x + ct, that is, have the form H(x + ct). Then, to solve the first (inhomogenous) equation relating v to u, we can note that its homogenous solution must be a function of the form F(x - ct), by logic

  3. Duhamel's principle - Wikipedia

    en.wikipedia.org/wiki/Duhamel's_principle

    Duhamel's principle also holds for linear systems (with vector-valued functions u), and this in turn furnishes a generalization to higher t derivatives, such as those appearing in the wave equation (see below). Validity of the principle depends on being able to solve the homogeneous problem in an appropriate function space and that the solution ...

  4. List of equations in fluid mechanics - Wikipedia

    en.wikipedia.org/wiki/List_of_equations_in_fluid...

    F•dS is the component of flux passing through the surface, multiplied by the area of the surface (see dot product). For this reason flux represents physically a flow per unit area . Here t ^ {\displaystyle \mathbf {\hat {t}} \,\!} is a unit vector in the direction of the flow/current/flux.

  5. Helmholtz equation - Wikipedia

    en.wikipedia.org/wiki/Helmholtz_equation

    The Helmholtz equation has a variety of applications in physics and other sciences, including the wave equation, the diffusion equation, and the Schrödinger equation for a free particle. In optics, the Helmholtz equation is the wave equation for the electric field. [1] The equation is named after Hermann von Helmholtz, who studied it in 1860. [2]

  6. d'Alembert's formula - Wikipedia

    en.wikipedia.org/wiki/D'Alembert's_formula

    The solution of the above equation is given by the formula: (,) = ((+) + ()) + + + + (,). If g ( x ) = 0 {\displaystyle g(x)=0} , the first part disappears, if h ( x ) = 0 {\displaystyle h(x)=0} , the second part disappears, and if f ( x ) = 0 {\displaystyle f(x)=0} , the third part disappears from the solution, since integrating the 0-function ...

  7. List of equations in quantum mechanics - Wikipedia

    en.wikipedia.org/wiki/List_of_equations_in...

    Defining equation SI unit Dimension Wavefunction: ψ, Ψ To solve from the Schrödinger equation: varies with situation and number of particles Wavefunction probability density: ρ = | | = m −3 [L] −3: Wavefunction probability current: j: Non-relativistic, no external field:

  8. List of nonlinear partial differential equations - Wikipedia

    en.wikipedia.org/wiki/List_of_nonlinear_partial...

    Name Dim Equation Applications Landau–Lifshitz model: 1+n = + Magnetic field in solids Lin–Tsien equation: 1+2 + = Liouville equation: any + = Liouville–Bratu–Gelfand equation

  9. Planck relation - Wikipedia

    en.wikipedia.org/wiki/Planck_relation

    The Planck relation [1] [2] [3] (referred to as Planck's energy–frequency relation, [4] the Planck–Einstein relation, [5] Planck equation, [6] and Planck formula, [7] though the latter might also refer to Planck's law [8] [9]) is a fundamental equation in quantum mechanics which states that the energy E of a photon, known as photon energy, is proportional to its frequency ν: =.