# Electromagnetic spectrum

The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

Class   Wave-
length

${\displaystyle \lambda }$
Freq-
uency

${\displaystyle f}$
Energy per
photon

${\displaystyle E}$
Ionizing
γ Gamma rays   1 pm 300 EHz 1.24 MeV
10 pm 30 EHz 124 keV
HX Hard X-rays
100 pm 3 EHz 12.4 keV
SX Soft X-rays
1 nm 300 PHz 1.24 keV
10 nm 30 PHz 124 eV
EUV Extreme
ultraviolet
100 nm 3 PHz 12.4 eV
NUV Near ultraviolet,
visible
1 μm 300 THz 1.24 eV
NIR Near infrared
10 μm 30 THz 124 meV
MIR Mid infrared
100 μm 3 THz 12.4 meV
FIR Far infrared
1 mm 300 GHz 1.24 meV
Micro-
waves

and

waves
EHF Extremely high
frequency
1 cm 30 GHz 124 μeV
SHF Super high
frequency
1 dm 3 GHz 12.4 μeV
UHF Ultra high
frequency
1 m 300 MHz 1.24 μeV
VHF Very high
frequency
10 m 30 MHz 124 neV
HF High
frequency
100 m 3 MHz 12.4 neV
MF Medium
frequency
1 km 300 kHz 1.24 neV
LF Low
frequency
10 km 30 kHz 124 peV
VLF Very low
frequency
100 km 3 kHz 12.4 peV
ULF Ultra low
frequency
1 Mm 300 Hz 1.24 peV
SLF Super low
frequency
10 Mm 30 Hz 124 feV
ELF Extremely low
frequency
100 Mm 3 Hz 12.4 feV
Sources: File:Light spectrum.svg[1][2][3]

The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length.[4] Gamma rays, X-rays, and high ultraviolet are classified as ionizing radiation as their photons have enough energy to ionize atoms, causing chemical reactions.

In most of the frequency bands above, a technique called spectroscopy can be used to physically separate waves of different frequencies, producing a spectrum showing the constituent frequencies. Spectroscopy is used to study the interactions of electromagnetic waves with matter.[5] Other technological uses are described under electromagnetic radiation.