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The standard example of a longitudinal wave is a sound wave or "pressure wave" in gases, liquids, or solids, whose oscillations cause compression and expansion of the material through which the wave is propagating. Pressure waves are called "primary waves", or "P-waves" in geophysics. Water waves involve both longitudinal and transverse motions ...
The most widely used is the AB magnitude system, [15] in which photometric zero points are based on a hypothetical reference spectrum having constant flux per unit frequency interval, rather than using a stellar spectrum or blackbody curve as the reference. The AB magnitude zero point is defined such that an object's AB and Vega-based ...
It is defined as periodic time increase per unit time; it is a dimensionless quantity, but can be given the units of s⋅s −1 (seconds per second). [ 59 ] The spin-down rate ( P -dot) of neutron stars usually falls within the range of 10 −22 to 10 −9 s⋅s −1 , with the shorter period (or faster rotating) observable neutron stars ...
Second-harmonic generation (SHG), also known as frequency doubling, is the lowest-order wave-wave nonlinear interaction that occurs in various systems, including optical, radio, atmospheric, and magnetohydrodynamic systems. [1] As a prototype behavior of waves, SHG is widely used, for example, in doubling laser frequencies.
dBm or dB mW (decibel-milliwatts) is a unit of power level expressed using a logarithmic decibel (dB) scale respective to one milliwatt (mW). It is commonly used by radio, microwave and fiber-optical communication technicians & engineers to measure the power of system transmissions on a log scale , which can express both very large and very ...
This was an official unit of measurement in South Africa until the 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1 morgen = 0.856 532 hectares. [28] This unit of measure was also used in the Dutch colonial province of New Netherland (later New York and parts of New England). [29] [30]
The maximum work is thus regarded as the diminution of the free, or available, energy of the system (Gibbs free energy G at T = constant, P = constant or Helmholtz free energy F at T = constant, V = constant), whilst the heat given out is usually a measure of the diminution of the total energy of the system (internal energy).
A megatsunami is a tsunami with an initial wave amplitude measured in many tens or hundreds of metres.The term "megatsunami" has been defined by media and has no precise definition, although it is commonly taken to refer to tsunamis over 100 metres (330 ft) high. [2]