Negative frequency Negative frequency The concept of negative and positive frequency can be as simple as a wheel rotating one way or the other way: a "signed value" of frequency can indicate both the rate and direction of rotation. The rate is expressed in units such as revolutions (a.k.a. "cycles") per second (hertz) or radian/second (where 1 cycle corresponds to 2"π" radians). Let "ω" be a nonnegative parameter with units of radians/sec. Then the angular function (angle vs. time) , has slope −"ω", which is called a negative frequency. But when the function is used as the argument of a cosine operator,
Rayleigh (unit) Rayleigh (unit) The rayleigh is a unit of photon flux, used to measure airglow (auroras, for example). It was first proposed in 1956 by Donald M. Hunten, Franklin E. Roach, and Joseph W. Chamberlain. It is named for John William Strutt, 3rd Baron Rayleigh (1842–1919). Its symbol is R (also used for the röntgen, an unrelated unit). SI prefixes are used with the rayleigh. One rayleigh (1 R) is defined as a column emission rate of 10 photons per square metre per column per second. Note that rayleigh is an apparent emission rate, as no allowances have been made for