The electromagnetic spectrum is a summary of all the possible frequencies of energy that result from the interaction between magnetic and electrical fields. There is a continuous transition from one frequency to another and that is why it is called a spectrum. For convenience when dealing with the spectrum it is divided into broad categories based on the most common applications.
Most of the spectrum is invisible to the human eye and ranges from very low frequency electrical and radio waves to very high frequency gamma rays. As the frequency increases, the wavelength decreases with the two being related by the equation c = frequency * wavelength where c is the speed of light (3 x 10^8 m/s) which is considered constant.
The energy is proportional to the wavelength based on the equation E = hf, where E is the energy, h is Planck's constant, and f is the frequency in Herz. Thus, the lowest frequency waves in the electromagnetic spectrum have the lowest energy while the highest frequency waves have the highest energy.
The electromagnetic spectrum includes all frequencies of electromagnetic radiation, from the radiowaves, which have a long wavelength, to gamma rays which have a short wavelength. It is referred to as a spectrum, but divided up by the ways the radiation interacts with matter. From longest to shortest wavelengths, the spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-Rays, gamma rays. Electromagnetic radiation in the range of 380-760nm is detected by the human eye and is known as visible light. The color red is at the longer end of the visible spectrum and the color violet is at the shorter end. All other wavelengths that are greater than 760nm and less than 380nm are not visible to the human eye.
Electromagnetic spectrum refers to the entire range of electromagnetic waves, which are related patterns of electric and magnetic forces. These waves are generated by oscillation of electric charges. Visible light waves, which were the the first of the electromagnetic waves to be identified as waves, constitute one one small part within the entire spectrum of electromagnetic waves. The name spectrum was first applied to the range of these light waves. Beyond the violet end of the visible spectrum exist ultraviolet rays, X rays, and gamma rays. Beyond the red end of the visible spectrum exist infrared rays and radio waves.
Electromagnetic spectrum consists of bands of different wavelengths. In order of increasing wavelengths, these include gamma rays, X rays, ultraviolet light, visible light, infrared rays, microwaves, and radio waves.