amplitude

[tripkramer]

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I've read that amplitude is independent of frequency, wavelength, and velocity of a wave. I've also read that in resonance (natural frequency), the system vibrates at a maximum amplitude (I'm guessing this is from the equation Intensity=f^2 x a^2 x v?)?

So when is it independent and when is it dependent? Maybe it differs because the first situation is light and the second is sound?

Thank you.

 

[milski]

When they say that the amplitude is independent, they mean that for a given media you will always have a relation between speed, frequency and wavelength, v=const=λf but the amplitude can be arbitrary.

In the case of resonance, you superimpose a number of waves and the resulting amplitude depends on their frequencies. The resultant wave can still have arbitrary amplitude (by changing the amplitude of the initial waves) but its frequency and wavelength are still "locked" in the equation above.

 

[DrBTS]

I like to think of amplitude as the y directional value while frequency is a dependent property on wavelength.