For thousands of years, humans were looking up at the star-studded night sky using just their eyes sensitive to the optical wavelength of the electromagnetic spectrum.The first telescopes ...

Learn about the electromagnetic spectrum, ... Radio waves have the longest wavelengths of all EM waves. Radio waves have wavelengths ranging from thousands of metres down to around 30 cm.

X-rays have even shorter wavelengths and are used by doctors to see inside our bodies. Gamma rays have the shortest wavelengths. They are produced by nuclear reactions and are used to treat cancer.

Radio waves are the longest wavelength emissions on the electromagnetic spectrum, meaning that the distance between two peaks of the wave is relatively far apart.