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I came across this amplitude equation from this website : http://formulas.tutorvista.com/physics/amplitude-formula.html It states that 'amplitude = distance / frequency'. This means that as the distance covered by the wave increases, the amplitude increases. It does not seem quite right to me. Can anyone explain the logic of this equation?

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No, I can't, because that formula is nonsense. Furthermore, referring to the first paragraph of you link:

  • Amplitude is not the measure of change over a single period.
  • The maximum height is the amplitude, assuming the wave is a physical displacement wave. But there are many waves that are not: electromagnetic waves, for example.
  • Amplitude may be expressed in dB, but usually isn't, and if it is, one must provide the reference amplitude.

The formula given is wrong. It is not even dimensionally correct. It equates meters with meters/Hz.

Example 2. isn't even wrong. dB is dimensionless, while example 2 has it with units meters/Hz.

Take that web site off of your bookmarks.

update

I poked around that website. The physics descriptions and explanations are garbled at best. Many entries are in poor English grammar, which can lead to ambiguities and wrong conclusions. There are many good sites on the Internet; that one is not one of them. There are also poor sites, and it's impossible for the novice to know which is which unless the writing is so bad as to be useless. You'll have to look at several and see if you can find some kind of consensus.

This problem is not limited to web sites. I'm teaching from a textbook that has mistakes, in one case it has two statements that contradict each other. These two statements are separated by six lines of text!

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  • $\begingroup$ My advice for a reliable website for formulas is. Have a search for "hyperphysics" and save the link. $\endgroup$
    – Jitter
    Oct 5, 2015 at 14:50
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From the information given on the "tutorvista" site, it appears that the information and the equation is rather garbled. I would not use this website. You might want to ask Physics Stack about the problem you are working on where you are trying to find out something about a wave.

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