We use the relation between frequency, speed and wavelength as
.
Here,
is wavelength , f is frequency and v is speed.
Given
and we take the speed of sound in aluminium,
.
Substituting these values in above relation, we get
![\lambda = (5100 \ m/s)/(2.8 \ MHz ) = (5100 \ m/s)/( 2.8 * 10 ^6 Hz) = 1821.43 * 10^(-6) m](https://img.qammunity.org/2019/formulas/physics/college/gpibmfsl7kyux3iwbuvyla5gvvmbf4g4jf.png)
Thus , the wavelength of given ultrasound wave traveling through aluminum is
![1821.43 * 10^(-6) \ m = 0.001821 \ m = 1.82 \ mm](https://img.qammunity.org/2019/formulas/physics/college/7k9rvryif34exlhrogxp3r2fykil2qks86.png)