The form of radiation with the longest wavelength is radio waves. Radio waves have wavelengths ranging from several millimeters to kilometers, making them the longest wavelength form of electromagnetic radiation.
Radio waves are a type of electromagnetic radiation that is commonly used for communication and broadcasting, such as in radio and television transmissions. They are also used in technologies like Wi-Fi, cellular communication, and radar systems.
As we move along the electromagnetic spectrum from radio waves to shorter wavelengths, we encounter other forms of radiation, such as microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Each of these forms of radiation has progressively shorter wavelengths and higher energy compared to the previous one.