The Physics
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Opus in profectus

Electromagnetic Spectrum

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Introduction

A good, general sequence to remember is radio waves, microwaves, infrared, light, ultraviolet, x-rays, gamma rays

Spectrum chart

open in a new scrollable landscape/portrait window

micropulsations

Less than 3 Hz is subradio, micropulsations, or another name.

radio waves

3 Hz–3 THz seems to be the agreed upon range of frequencies.

Radio bands Adapted from: ITU, 2025
frequency
band name		 frequency
range		 ITU band
number		 wavelength
band name		 wavelength
range
30 – 300 mHz −1 (10−1 Hz) gigametric 10 – 1 Gm
tremendously low frequency (TLF) 300 – 3000 mHz 0 (100 Hz) hectomegametric 1000 – 100 Mm
extremely low frequency (ELF) 3 – 30 Hz 1 (101 Hz) super-megametric waves 100 – 10 Mm
super low frequency (SLF) 30 – 300 Hz 2 (102 Hz) megametric waves 10 – 1 Mm
ultra low frequency (ULF) 300 – 3000 Hz 3 (103 Hz) sub-megametric waves 1000 – 100 km
very low frequency (VLF) 3 – 30 kHz 4 (104 Hz) super-kilometric waves 100 – 10 km
low frequency (LF) 30 – 300 kHz 5 (105 Hz) kilometric waves 10 – 1 km
medium frequency (MF) 300 – 3000 kHz 6 (106 Hz) hectometric waves 1000 – 100 m
high frequency (HF) 3 – 30 MHz 7 (107 Hz) decametric waves 100 – 10 m
very high frequency (VHF) 30 – 300 MHz 8 (108 Hz) metric waves 10 – 1 m
ultra high frequency (UHF) 300 – 3000 MHz 9 (109 Hz) decimetric waves 1000 – 100 mm
super high frequency (SHF) 3 – 30 GHz 10 (1010 Hz) centimetric waves 100 – 10 mm
extremely high frequency (EHF) 30 – 300 GHz 11 (1011 Hz) millimetric waves 10 – 1 mm
 tremendously high frequency (THF)  300 – 3000 GHz  12 (1012 Hz)  sub-millimetric waves 1000 – 100 μm 
3 – 30 THz 13 (1013 Hz) centimillimetric 100 – 10 μm
30 – 300 THz 14 (1014 Hz) micrometric 10 – 1 μm
300 – 3000 THz 15 (1015 Hz) decimicrometric 1000 – 100 nm

microwaves

Short (less than a meter) to teeny tiny (but not less than a tenth of a millimeter) wavelength radio waves. The high frequency side of the radio spectrum 0.3–3,000 GHz. Where the microwaves end and infrared begins is open to some debate however.

Diagram

Text

Circuit diagram

Equivalent Circuit Diagram

Equivalent circuit diagram

Diagram from Percy Spencer's 1945 US patent for the microwave oven. Note the popcorn kernel labeled "Food to be Cooked".

Radar bands * German for short
† Space radiocommunication
‡ Unconfirmed
§ 2.700–3.600 in the Americas
 5.250–5.850 in the Americas
frequency range (GHz)      
band name IEEE ISO   ITU  
  HF   high frequency 0.003 – 0.03        
VHF very high frequency 0.03 – 0.3 0.138
0.216
0.223		 –
–
–		 0.144
0.225
0.230
UHF ultra high frequency 0.3 – 1 0.420
0.890		 –
–		 0.450
0.942
P previous 0.216 – 0.450 0.225 – 0.39 
L long 1 – 2 0.39 – 1.55 1.215
1.525		 –
–		 1.400
1.710†
S short 2 – 4 1.55 – 5.2 2.300
2.500
2.700		 –
–
–		 2.500
2.690†
3.700§
C compromise 4 – 8 3.9 – 6.2 3.400
4.200
4.500
5.250
5.850		 –
–
–
–
–		 4.200†
4.400
4.800†
5.925
7.075†
X crosshair 8 – 12 5.2 – 10.9 8.500 – 10.68
uKu kurze* under 12 – 18 10.70
13.40
14.00
15.40		 –
–
–
–		 13.25†
14.00
14.50†
17.70
K kurze* 18 – 27 10.9 – 36 17.70
24.05
24.65		 –
–
–		 20.20†
24.25
24.75‡
aKa kurze* above 27 – 40 27.50
33.40		 –
–		 30.00†
36.00
Q 36 – 46
V 40 – 75 46 – 56 37.50
47.20
59.00		 –
–
–		 42.50†
50.20†
64.00‡
W 75 – 110 56 – 100 76.0
92.0		 –
–		  81.0‡
100.0‡
mm millimeter 110 – 300 136.0
151.5
231.0
238.0		 –
–
–
–		 148.5‡
155.5‡
235.0‡
248.0‡
THz terahertz 300 – 1000 300 – 3000‡

The traditional radar band names (L, S, C, X, Ku, K and Ka) originated during World War II as a secret code so scientists and engineers could talk about classified frequencies without divulging them. After the war the codes were declassified and the Q, V, W, and millimeter (mm) bands were added. The designations were eventually adopted by the Institute of Electrical and Electronics Engineers (IEEE — read as "I triple E") in the United States, and internationally by the International Organization for Standardization (ISO) and International Telecommunication Union (ITU).

infrared

Literally "below" red. So anything shorter than red light (700–800 nm or ~400 THz), but not so short that you could build an oscillating circuit transmitter; i.e., a radio (1 mm or 3 THz). Actually, the longer wavelengths kind of drip over into microwaves.

light (a.k.a."visible light")

Roughly 400–700 nm

ultraviolet

Literally "beyond" violet. So shorter than say 400 nm. Somewhere around there. Down to as short as 1 nm in some fields of science. (Ultraviolet and x-rays overlap.) Whether you label it ultraviolet or x-rays depends on the application.

near, mid, far

A, B, C

Where does it all end?

Spectral regions for optical radiation Adapted from: CIE; ISO
bands and sub‑bands wavelength
range (nm)		 frequency
range (THz)
 optical radiation  1,000,000 – 1 0.3 – 300,000
infrared radiation (IR) 1,000,000 – 760 0.3 – 395
⎧
⎪
⎪
⎨
⎪
⎪
⎩
infrared-C (IR-C) 1,000,000 – 3,000 0.3 – 100
infrared-B (IR-B) 3,000 – 1,400 100 – 214
infrared-A (IR-A) 1,400 – 760 214 – 395
⎧
⎪
⎪
⎨
⎪
⎪
⎩
far infrared (FIR) 1,000,000 – 3,000 0.3 – 100
middle infrared (MIR) 3,000 – 1,400 100 – 214
near infrared (NIR) 1,400 – 760 214 – 395
visible radiation 830 – 360 361 – 833
for spectral color bands see color
ultraviolet radiation (UV) 400 – 1 750 – 300,000
⎧
⎪
⎪
⎨
⎪
⎪
⎩
ultraviolet A (UVA) 400 – 315 750 – 952
ultraviolet B (UVB) 315 – 280 952 – 1,070
ultraviolet C (UVC) 280 – 100 1,070 – 3,000
⎧
⎪
⎪
⎪
⎪
⎨
⎪
⎪
⎪
⎪
⎩
near ultraviolet (NUV) 400 – 300 750 – 1,000
middle ultraviolet (MUV) 300 – 200 1,000 – 1,500
far ultraviolet (FUV) 200 – 122 1,500 – 2,460
Lyman alpha line (Ly-α) 122 – 121 2,460 – 2,480
extreme ultraviolet (EUV) 121 – 10 2,480 – 30,000
vacuum ultraviolet (VUV) 200 – 10 1,500 – 30,000
      soft x‑ray and EUV (XUV) 121 – 0.1 2,480 – 3,000,000 

x-rays

The range of wavelengths here is 10−8 m down to 10−12 m, with the long end overlapping the ultraviolet and the short end overlapping gamma rays,

gamma rays

Everything shorter than 10−11 meter. How much shorter? Good question.