What has the longest wavelength on the electromagnetic spectrum?

Radio waves have the longest wavelengths on the electromagnetic spectrum.

Here are a few key characteristics of radio waves:

• Wavelength: They can range from about 1 millimeter to over 100 kilometers long—sometimes even larger than our planet.
• Frequency and Energy: Because wavelength and frequency are inversely related, radio waves have the lowest frequencies and the lowest energy of all electromagnetic radiation.
• Applications: They are widely used for communication, including television broadcasting, FM and AM radio, mobile phone networks, and radar systems.