The frequency of a wave is the reciprocal of its period, so for the wave in this problem, its frequency is
![f= (1)/(T)= (1)/(0.0125 s) =80 Hz](https://img.qammunity.org/2019/formulas/physics/high-school/n4av7msi1xrul3ms9jzoiyp9jqp6svqzb1.png)
The basic relationship between wavelength, frequency and speed of a wave is given by:
![\lambda= (v)/(f)](https://img.qammunity.org/2019/formulas/physics/high-school/gfclosvkshm2gzbr67ejccjp87ffyj4ctr.png)
where
![\lambda](https://img.qammunity.org/2019/formulas/physics/college/xkhb3hdgeg4aavb9pvg1c4kt14yl6rgqn5.png)
is the wavelength of the wave
v is its speed
f is its frequency
If we plug the numbers given by the problem into this equation, we can find the wavelength of this wave:
![\lambda= (v)/(f)= (3.26 \cdot 10^6 m/s)/(80 Hz)=4.08 \cdot 10^4 m=40.8 km](https://img.qammunity.org/2019/formulas/physics/high-school/8ckzcifw3k7pbjc54d72wqndsej0cuipid.png)