Hello, I confused as there are 2 very similar equation but I do not know when to use each of them. They are:(adsbygoogle = window.adsbygoogle || []).push({});

[itex]f = \frac{v}{\lambda}[/itex] and [itex]f = \frac{c}{\lambda}[/itex].

What is the difference between [itex]c[/itex] and [itex]v[/itex] and when can the appropriate one be used?

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# Wavelength, Frequency

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