What is the electromagnetic spectrum???

Answer 1

The Electomagnetic spectrum is really a plot which indicates the radiative distribution according to the spacing between micromasses and frequency at which their motion takes place.
This radiation Spectrum indicates ,and also includes the range of the visible spectrum of light that enables our eyes to sense.

Answer 2

A spectrum is just a range of something, like frequencies. The term is usually limited to electro-magnetic (EM) frequencies, but not always. Sound, for example, also has a spectrum of frequencies called tones. Or we hear something like a full spectrum of emotions for example.

EM energies are found by E = hf; where h is Plank's constant and f is a discrete frequency. The following table is a brief Spectrum of Electromagnetic Radiation:

Region ..Wavelength(centimeters).... Frequency(Hz)
Radio ...........< 3 x 10^9 .........................< 10^-5
Visible............. 7 - 4 x 10^-5 ...............4.3 - 7.5 x 10^14
Gamma Rays.....< 10^-9....................... > 3 x 10^19 [See source.]

From E = hf, can see from the brief table, gamma rays from outer space have E/e = hF/hf = 10^19/10^-5 = 10^24 times more energy per quantum than radio waves. F is a typical gamma ray frequency (Hz) and f is a typical radio wave frequency. Radar, microwaves, TV, X-rays, and so on make up other bands of frequencies along the EM spectrum. Their one common point is that they are all photon based forces.