Answer:
f = 23.43 Hz for radio waves.
Step-by-step explanation:
In this case, we need to find the frequency of an electromagnetic wave having a wavelength equal to Earth’s diameter i.e. 12,800 km. The relation between the frequency, wavelength and the speed is given by :
![v=f\lambda](https://img.qammunity.org/2021/formulas/physics/college/gxt5v14463fb3oaf6o1vvzedg8rdrff0c7.png)
Electromagnetic wave moves with a speed of light
![c=f\lambda](https://img.qammunity.org/2021/formulas/physics/high-school/2yb9modtin2v49rpvhtimpqykq47m2vyy3.png)
![f=(c)/(\lambda)](https://img.qammunity.org/2021/formulas/physics/college/c9bym2s2rzlu01a7rb77ey8lhpcre10i6a.png)
![f=(3* 10^8)/(12800* 10^3)](https://img.qammunity.org/2021/formulas/physics/college/dqrz2f4pf9u17pxks364fz649h25npazzy.png)
f = 23.43 Hz
So, the frequency of an electromagnetic wave is 23.43 Hz. It belongs to radio waves.