Its meaning is the number of times that a substance completes periodic changes in 1s, which is called frequency, which is usually represented by the letter f and the physical unit is Hz. T is the period. The concept of frequency is not only used in mechanics and acoustics, but also in electromagnetism, optics and radio technology.

Frequency calculation formula of known wavelength and wave velocity:

f=V/λ.

In the formula, f stands for frequency, v stands for wave velocity and λ stands for wavelength.

For example, the propagation speed of sound wave with a wavelength of 322nm in air is 320m/s, and the frequency of this wave is found.

Convert wavelength units to meters. If the unit of wavelength is known as nanometer, it needs to be converted into meter. The method is to divide by multiples of meters and nanometers.

λ= 322nm = 322 nmx( 1m/ 109nm)= 3.22 x 10-7m = 0.000000322m .

Divide the wave velocity by the wavelength. The frequency f can be obtained by dividing the wave velocity v by the wavelength λ in meters.

When v is the speed of light, that is, when calculating the frequency in vacuum, V=C, then the formula of frequency in vacuum is: f=C/λ.