# frequency

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## frequency

frequency: see harmonic motion; wave.

## Frequency (wave motion)

The number of times which sound pressure, electrical intensity, or other quantities specifying a wave vary from their equilibrium value through a complete cycle in unit time. The most common unit of frequency is the hertz (Hz), which is equal to 1 cycle per second. In one cycle there is a positive variation from equilibrium, a return to equilibrium, then a negative variation, and return to equilibrium. This relationship is often described in terms of the sine wave, and the frequency referred to is that of an equivalent sine-wave variation in the parameter under discussion. See Frequency measurement, Sine wave, Wave motion

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

## frequency

Symbol: f , ν. The number of oscillations per unit time of a vibrating system. Frequency is measured in hertz. The frequency of a wave is the number of wave crests passing a point per unit time. For light and other electromagnetic radiation, it is related to wavelength λ by ν = c /λ, where c is the speed of light.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Frequency

The frequency of an event A is the ratio m/n of the number m of occurrences of A in a given series of trials to the total number n of trials. If the trials are independent and there is a definite probability p of the occurrence of A in an individual trial, then, for arbitrarily small ∊ > 0, at sufficiently large m it is practically certain that the frequency m/n satisfies the inequality

(seeLARGE NUMBERS, LAW OF and PROBABILITY).

The term “frequency” is used in mathematical statistics to designate the number of elements of a set that have a specified attribute.

## frequency

[′frē·kwən·sē]
(physics)
The number of cycles completed by a periodic quantity in a unit time.
(statistics)
The number of times an event or item falls into or is expected to fall into a certain class or category.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## frequency

The number of oscillations per second (a) of the current or voltage in an alternating-current electric circuit, or (b) of a sound wave, or (c) of a vibrating solid object; expressed in hertz (abbr. Hz) or in cycles per second (abbr. cps).
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

## frequency

i. The number of recurrences of a periodic phenomenon in a unit of time.
ii. The number of cycles completed in one second. One cycle per second is the basic unit of measurement of frequency and is called a hertz.
iii. The number of services operated by an airline per day or per week over a particular route.

## frequency

1. Physics the number of times that a periodic function or vibration repeats itself in a specified time, often 1 second. It is usually measured in hertz.
2. Ecology
a. the number of individuals of a species within a given area
b. the percentage of quadrats that contains individuals of a species
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

## frequency

The number of oscillations (vibrations) in one second. Frequency is measured in Hertz (Hz), which is the same as "oscillations per second" or "cycles per second." For example, the alternating current in a wall outlet in the U.S. and Canada is 60Hz. Electromagnetic radiation is measured in kiloHertz (kHz), megahertz (MHz) and gigahertz (GHz). See wavelength, frequency response, audio, carrier and space/time.

Frequency The frequency is the number of oscillations per second. The higher the frequency (the closer the ripples would be in this diagram) and the shorter the wavelength.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in classic literature ?
In the remote earliest form of the stories, as Celtic myths, this supernatural element was no doubt frank and very large, but Malory's authorities, the more skeptical French romancers, adapting it to their own age, had often more or less fully rationalized it; transforming, for instance, the black river of Death which the original heroes often had to cross on journeys to the Celtic Other World into a rude and forbidding moat about the hostile castle into which the romancers degraded the Other World itself.
The sentences are often long, but always 'loose' and clear; and short ones are often used with the instinctive skill of sincerity.
I am a curious person to attach oneself to, Paterson; don't you see that even David often smiles at me when he thinks he is unobserved.
When I returned, as often as it was necessary, I cleared their path from the snow and performed those offices that I had seen done by Felix.
Vane, also (the brother), seems to have the same prejudices, and when I tell him, as I often think it right to do, that his sister is not his subordinate, even if she does think so, but his equal, and, perhaps in some respects his superior, and that if my brother, in Bangor, were to treat me as he treates this poor young girl, who has not spirit enough to see the question in its true light, there would be an indignation, meeting of the citizens to protest against such an outrage to the sanctity of womanhood--when I tell him all this, at breakfast or dinner, he bursts out laughing so loud that all the plates clatter on the table.
He is very learned, and has a great desire for information; he appreciates a great many of my remarks, and after dinner, in the salon, he often comes to me to ask me questions about them.
Many children of the tenderest years were compelled then, as is now true I fear, in most coal-mining districts, to spend a large part of their lives in these coal-mines, with little opportunity to get an education; and, what is worse, I have often noted that, as a rule, young boys who begin life in a coal-mine are often physically and mentally dwarfed.
Looked at from this standpoint, I almost reached the conclusion that often the Negro boy's birth and connection with an unpopular race is an advantage, so far as real life is concerned.
Having alluded to the subject of reversion, I may here refer to a statement often made by naturalists--namely, that our domestic varieties, when run wild, gradually but certainly revert in character to their aboriginal stocks.
Domestic races of the same species, also, often have a somewhat monstrous character; by which I mean, that, although differing from each other, and from the other species of the same genus, in several trifling respects, they often differ in an extreme degree in some one part, both when compared one with another, and more especially when compared with all the species in nature to which they are nearest allied.
The queen, who often used to hear me talk of my sea-voyages, and took all occasions to divert me when I was melancholy, asked me whether I understood how to handle a sail or an oar, and whether a little exercise of rowing might not be convenient for my health?
The two pilgrims, often pressing each other's hands, or exchanging a smile or cheerful look, pursued their way in silence.

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