Radio waves and visible light are both forms of electromagnetic radiation, so they both travel at the speed of light in vacuum. What makes them different are their wavelengths (or synonymously their frequencies).The wavelengths of visible light span from about 390-700 nm, and the frequency from 430 to 790 THz.The wavelengths of radio waves go from about 1 mm to 100 km, and frequencies between 3 kHz and 300 GHz.The different sized wavelengths also give rise to slightly different properties. For example, since radio waves have a longer wavelength and lower frequencies, they are less energetic than visible light. Recall:Elight=hν=hcλ
where Elight is the energy of the light, h is Planck's constant, c is the speed of light, νis the frequency of light, and λ is the wavelength
