Here's why:

* Electromagnetic Spectrum: The electromagnetic spectrum encompasses all types of electromagnetic radiation, arranged by their wavelengths (or equivalently, their frequencies).

* Wavelength and Frequency: Wavelength and frequency are inversely proportional. Longer wavelengths correspond to lower frequencies.

* Radio Waves: Radio waves occupy the lowest frequency (and therefore longest wavelength) portion of the electromagnetic spectrum. They range from a few millimeters to tens of kilometers.

Examples of radio waves include:

* AM and FM radio broadcasts

* TV signals

* Cell phone signals

* Satellite communications

* Radar

Let me know if you'd like to learn more about any of these topics!