Here's why:

* Electromagnetic Spectrum: Microwaves are part of the electromagnetic spectrum, which includes various types of radiation arranged by wavelength and frequency.

* Wavelength and Frequency Relationship: Wavelength and frequency are inversely proportional. This means that longer wavelengths correspond to lower frequencies and vice versa.

* Radio Waves: Radio waves have the longest wavelengths in the electromagnetic spectrum, with wavelengths ranging from millimeters to kilometers. This is why radio antennas need to be large to effectively receive these long waves.

Here's a simplified way to remember it:

* Long Waves: Radio waves are the "long distance runners" of the electromagnetic spectrum.

* Short Waves: Microwaves are shorter than radio waves but longer than infrared radiation.

So, while microwaves are used in everyday appliances, they don't have the longest wavelengths. That distinction belongs to radio waves.