LexNotebook - F

Frequency
In physics, the frequency of a wave is the number of wave crests that pass a point in one second (A wave crest is the peak of the wave). Hertz (symbol Hz) is the unit of frequency. where v is speed and (Lambda) is wavelength. The formula for the frequency of light waves is
$f = c/ \lambda$
where the c is the speed of light.


First of all:
“First of all” makes sense when you want to emphasize the primacy of the first item in a series, but it should not be followed by “second of all,” where the expression serves no such function. And “secondly” is an adverbial form that makes no sense at all in enumeration (neither does “firstly”). As you go through your list, say simply “second,” “third,” “fourth,” etc.
(from this site)

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