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In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light).The opposite change, a decrease in wavelength and increase in frequency and energy, is known as a blueshift, or negative redshift.
The phase speed – and thus also the wavelength L = c p T – decreases monotonically with decreasing depth. However, the group velocity first increases by 20% with respect to its deep-water value (of c g = 1 / 2 c 0 = gT/(4π)) before decreasing in shallower depths. [1]
The GPS satellite gravitational blueshift velocity equivalent is less than 0.2 m/s, which is negligible compared to the actual Doppler shift resulting from its orbital velocity. In astronomical objects with strong gravitational fields the redshift can be much greater; for example, light from the surface of a white dwarf is gravitationally ...
Doppler shift of the direct path can be estimated by the following formula: [22], = where is the speed of the mobile station, is the wavelength of the carrier, is the elevation angle of the satellite and is the driving direction with respect to the satellite.
The wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests (on top), or troughs (on bottom), or corresponding zero crossings as shown. In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats.
If an inertial observer looks at an accelerating clock, only the clock's instantaneous speed is important when computing time dilation. [9] The converse, however, is not true. The analysis of scenarios where both objects are in accelerated motion requires a somewhat more sophisticated analysis. Not understanding this point has led to confusion ...
The relevant wave speed in the discussion above is the phase velocity of the wave. This is typically close to the group velocity which can be seen as the truer speed of a wave, but when they differ it is important to use the phase velocity in all calculations relating to refraction.
A pulse with different group and phase velocities (which occurs if the phase velocity is not the same for all the frequencies of the pulse) smears out over time, a process known as dispersion. Certain materials have an exceptionally low (or even zero) group velocity for light waves, a phenomenon called slow light . [ 73 ]