What is the electro magnetic spectrum?

Answer 1

Electrical charges in motion produce emission of electromagnetic waves, like radio waves we use for cell phones and radio programs, millimeter waves we use in radars, visible light, X-rays and gamma rays.

All the above forms of electromagnetic radiation differs from their frequency, in particular I have listed them in order of increasing frequency (and decreasing wavelength).

When a real wave is emitted a set of frequencies are emitted, almost never a single frequency. Under a fundamental point of view this is due to the quantum mechanical indetermination principle. In practical cases, quite more important causes are the fluctuations in the speed of moving charges and the fact that their trajectory is not purely linear.

The set of frequencies that forms a practical wave is called electromagnetic spectrum of that wave.

The overall frequency axes is divided in zone, as listed below

Region

Wavelength (Angstroms)

Wavelength (centimeters)

Frequency (Hz)

Energy (eV)

Radio

> 109

> 10

< 3 x 109

< 10-5

Microwave

109 - 106

10 - 0.01

3 x 109 - 3 x 1012

10-5 - 0.01

Infrared

106 - 7000

0.01 - 7 x 10-5

3 x 1012 - 4.3 x 1014

0.01 - 2

Visible

7000 - 4000

7 x 10-5 - 4 x 10-5

4.3 x 1014 - 7.5 x 1014

2 - 3

Ultraviolet

4000 - 10

4 x 10-5 - 10-7

7.5 x 1014 - 3 x 1017

3 - 103

X-Rays

10 - 0.1

10-7 - 10-9

3 x 1017 - 3 x 1019

103 - 105

Gamma Rays

< 0.1

< 10-9

> 3 x 1019

> 105

Sub-zones are also defined.

Since the energy of a photon of an electromagnetic wave at a certain frequency f is proportional to the frequency by the equation

Energy= h f

where h is the Plank constant, higher the frequency, higher the phonons energy as indicated in the table (the energy of one electronvolt eV is the energy aquired by an electron when accelerated by a potential of one volt and it is equal to 1.6×10−19 joule).

Answer 2

The electromagnetic spectrum is the range of all types of electromagnetic radiation, including visible light, radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. These forms of energy differ in their wavelengths and frequencies, with longer wavelengths corresponding to lower frequencies and shorter wavelengths corresponding to higher frequencies.