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  2. Foucault's measurements of the speed of light - Wikipedia

    en.wikipedia.org/wiki/Foucault's_measurements_of...

    In 1834, Charles Wheatstone developed a method of using a rapidly rotating mirror to study transient phenomena, and applied this method to measure the velocity of electricity in a wire and the duration of an electric spark. [1] He communicated to François Arago the idea that his method could be adapted to a study of the speed of light.

  3. Fizeau experiment - Wikipedia

    en.wikipedia.org/wiki/Fizeau_experiment

    Fizeau used a special interferometer arrangement to measure the effect of movement of a medium upon the speed of light. According to the theories prevailing at the time, light traveling through a moving medium would be dragged along by the medium, so that the measured speed of the light would be a simple sum of its speed through the medium plus ...

  4. Michelson–Morley experiment - Wikipedia

    en.wikipedia.org/wiki/Michelson–Morley_experiment

    Physics theories of the 19th century assumed that just as surface water waves must have a supporting substance, i.e., a "medium", to move across (in this case water), and audible sound requires a medium to transmit its wave motions (such as air or water), so light must also require a medium, the "luminiferous aether", to transmit its wave ...

  5. Fizeau's measurement of the speed of light in air - Wikipedia

    en.wikipedia.org/wiki/Fizeau's_measurement_of_the...

    At the behest of the Paris Observatory under Urbain Le Verrier, Marie Alfred Cornu repeated Fizeau's 1848 toothed wheel measurement in a series of experiments from 1872 to 1876. The goal was to obtain a value for the speed of light accurate to one part in a thousand.

  6. Signal velocity - Wikipedia

    en.wikipedia.org/wiki/Signal_velocity

    Signal velocity is usually equal to group velocity (the speed of a short "pulse" or of a wave-packet's middle or "envelope"). However, in a few special cases (e.g., media designed to amplify the front-most parts of a pulse and then attenuate the back section of the pulse), group velocity can exceed the speed of light in vacuum, while the signal ...

  7. Ripple tank - Wikipedia

    en.wikipedia.org/wiki/Ripple_tank

    If a concave parabolic obstacle is used, a plane wave pulse will converge on a point after reflection. This point is the focal point of the mirror. Circular waves can be produced by dropping a single drop of water into the ripple tank. If this is done at the focal point of the "mirror" plane waves will be reflected back.

  8. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    A method of measuring the speed of light is to measure the time needed for light to travel to a mirror at a known distance and back. This is the working principle behind experiments by Hippolyte Fizeau and Léon Foucault. The setup as used by Fizeau consists of a beam of light directed at a mirror 8 kilometres (5 mi) away. On the way from the ...

  9. Wave velocity - Wikipedia

    en.wikipedia.org/wiki/Wave_velocity

    Phase velocity, the velocity at which a wave phase propagates; Pulse wave velocity, the velocity at which a pulse travels through a medium, usually applied to arteries as a measure of arterial stiffness; Group velocity, the propagation velocity for the envelope of wave groups and often of wave energy, different from the phase velocity for ...