Why is any wave defined by the wavelength, but not by the amplitude?

[Soumen2010]

Any wave is identified by its wavelength (or frequency), and the wavelength is the distance between the two consecutive crests (or troughs) in wave trains. But wave is not identified by its amplitude. The wave could have been described by the amplitude as it doesn't require two wave trains (or wave pulses). Can anybody explain why so?

 

[Fewmet]

Any wave is identified by its wavelength (or frequency), and the wavelength is the distance between the two consecutive crests (or troughs) in wave trains. But wave is not identified by its amplitude. The wave could have been described by the amplitude as it doesn't require two wave trains (or wave pulses). Can anybody explain why so?

That's not something I've ever considered. I suspect that the choice has to do with the phenomena that we focus on and what causes them. Color of light and pitch of sound are both a matter of frequency. Frequency is also at the heart of the Doppler effect and and beating. Amplitude primarily affect intensity...no other phenomena leap to mind.

 

[ashishsinghal]

Agree with Fewmet.

 

[DaleSwanson]

The frequency determines the properties of the wave. The amplitude just determines the magnitude of those properties. Knowing that two waves have equal amplitude, but different frequency doesn't really tell you a whole lot about how similar those waves are.

To use an analogy, in an atom the number of protons determines the properties of the element, and is thus used to describe the atom. On the other hand, the number of atoms is similar to amplitude of the wave. While knowing how many atoms you have is certainly important, it is more important to know what kind of atoms you have first.

 

[santo35]

Any wave is identified by its wavelength (or frequency), and the wavelength is the distance between the two consecutive crests (or troughs) in wave trains. But wave is not identified by its amplitude. The wave could have been described by the amplitude as it doesn't require two wave trains (or wave pulses). Can anybody explain why so?

well your question has the answer ! amplitude dosent require 2 wave trains ! the simple fact that often people are interested in motion of wave makes us "use" more often the terms frequency...
lemme xplain this. for describing amplitude you would just be done with a photograph of the wave . but insted if you want to know the frequency , you would need to see the wave moving ! and thus people could get more information out from frequency but people do use amplitude too...for defining a wave you surely need amplitude, its angular velocity and phase
y = A sin(\varpi*t + \varphi)...