The Electromagnetic Spectrum
The electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, X-rays, and gamma-rays.
Radiation of different wavelengths affects matter differently, for example overexposure to infrared radiation causes a “heat burn”, overexposure to visible and near ultraviolet light causes sun burn and sun tan, while overexposure to X ray radiation causes tissue damage.
These different effects are due to the ENERGY of the radiation.
Electromagnetic waves can not only be described by their wavelength, but also by their energy and frequency.
All three of these things are related to each other mathematically. This means that it is correct to talk about the energy of an X-ray or the wavelength of a microwave or the frequency of a radio wave. Radiation of high frequencies and short wavelengths are more energetic than radiation of lower frequencies and longer wavelengths. The quantitative relationship between frequency and energy was developed by Max Plank.
By studying black body radiation Max Plank developed the rudiments of the quantum theory of matter.