[fragmentary thoughts] thoughts on wavelength, wave velocity and period

【 twitter 】 About wavelength ｜ wave velocity ｜ The idea of a cycle

My understanding of physics has never been deep enough , Enough to take the exam without thinking , Today I heard an explanation about wavelength and wave velocity , I don't think it's right

Wavelength, velocity and period

wave velocity = wavelength * frequency , This is a formula that has been familiar since childhood , At least I started with this formula $$v=\lambda f$$

among v It's wave velocity ,lambda Is wavelength ,f It's the frequency

But now I think about it , I still don't feel right , The formula written in this way is easy to misunderstand beginners , Or to $$\lambda =\frac{v}{f}$$
The formula is more appropriate for getting started （ As explained below ）.

Calculation of wavelength

Wavelength is the property of a wave , There are two elements in the generation of waves , One is the medium of wave propagation , The second is the source of the wave . The medium of the former wave propagation determines the propagation speed of a wave , The speed of wave propagation is only related to the physical state of the medium （ temperature , Pressure, etc ）, The source of the latter wave determines how many times the wave oscillates up and down in one second .

Therefore, it is decided by the media first $v$, Then the vibration source determines the frequency $f$, Then we can calculate $\lambda =\frac{v}{f}$.

The vibration source completes a vibration period , cost $\frac{1}{f}$ Time , In the meantime , This vibration propagates a wavelength $\lambda$ Distance of .
And in unit time , Vibration source completion $f$ Secondary vibration ,“ launch ” 了 $f$ A complete wave , The first wave emitted has already spread $f\lambda$ Distance of . This distance is the distance of internal wave propagation per unit time , The distance is the wave velocity $v$, therefore $v=\lambda f$.