Here's why:

* Electromagnetic Spectrum: Radiation is a form of energy that travels in waves. The electromagnetic spectrum encompasses all types of radiation, from low-frequency radio waves to high-frequency gamma rays.

* Frequency and Wavelength: Frequency and wavelength are inversely proportional. This means that the lower the frequency, the longer the wavelength.

* Radio Waves: Radio waves have the lowest frequencies and the longest wavelengths within the electromagnetic spectrum.

Therefore, radio waves have the smallest frequency of all types of radiation.