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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 ...
Localized wave packets, "bursts" of wave action where each wave packet travels as a unit, find application in many fields of physics. A wave packet has an envelope that describes the overall amplitude of the wave; within the envelope, the distance between adjacent peaks or troughs is sometimes called a local wavelength.
The factor by which the speed is decreased is called the refractive index of the material. In a classical wave picture, the slowing can be explained by the light inducing electric polarization in the matter, the polarized matter radiating new light, and that new light interfering with the original light wave to form a delayed wave.
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. [1] [a] The hertz is an SI derived unit whose formal expression in terms of SI base units is s −1, meaning that one hertz is one per second or the reciprocal of one second. [2]
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]
A monochromatic wave (a wave of a single frequency) consists of successive troughs and crests, and the distance between two adjacent crests or troughs is called the wavelength. Waves of the electromagnetic spectrum vary in size, from very long radio waves longer than a continent to very short gamma rays smaller than atom nuclei.
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).
If the speed in the x direction varies with z, the tangential force in direction x per unit area normal to the z direction is =, where μ is the viscosity. This is also a flux, or flow per unit area, of x-momentum through the surface. [34]