The ebook FEEE - Fundamentals of Electrical Engineering and Electronics is based on material originally written by T.R. Kuphaldt and various co-authors. For more information please read the copyright pages.

Frequencies of Electromagnetic Oscillation

In principle, it is only practical to display the frequency spectrum in logarithmic form, since a range of 24 decimal powers, thus from 1 Hz to approximately 1024 Hz must be viewed. The frequency spectrum can be divided into four main ranges:

  • Low Frequency (LF, or AF for Audio Frequency)
  • High Frequency (HF, or RF for Radio Frequency)
  • The optical range with infrared (IR), visible light and ultraviolet light (UV)
  • The ionizing radiation (x-ray, γ-rays and cosmic rays)

The range of the main and subgroups except for visible light is specified by definition and therefore not based on physical phenomena. However, visible light can be observed very precisely within the wavelength range from 380 to 780 nm due to the spectral sensitivity of the human eye.

The high frequency range is considered to be complex, however this is based on three significant parameters:

  • the radiation of electromagnetic waves,
  • the duration of electrical signals and
  • the influence of electronic circuits by transmission lines and by coupling between different conductors.

If we take, for example, a thin, short wire with a diameter of 0.5 mm and a length of 5 mm for the signal transmission, then this will function excellently within the LF range. With increasing frequency, this piece of conductor line will start a considerable inductance until it achieves final radiation phenomena.

The electromagnetic spectrum with data of wavelength and frequency in a logarithmic representation from 0.1 Hz to 1024 Hz.


Therefore only micro strip lines or coaxial cables with a large mass or shielding surface can be used meaningfully for signal transmission starting from approximately 300 MHz. The electromagnetic wave here remains mainly in the low-loss substrate. Furthermore, starting with this frequency, wave and terminal resistors of lines play a role. When using RF components, good high-frequency grounding is necessary. This becomes the foundation for the functioning of an electronic circuit for increasing frequency.

A significant phenomenon in radio frequency technology is the radiation of waves into free space. If we compute the wavelength e.g. at 300 MHz, then we arrive at λ = 1m, hence at a magnitude which corresponds to objects in everyday life. Within the range of radio engineering, which became a substantial feature of our world today, not only cm-wave and m-waves are used, but also km-waves. Thus, the range of radio (high frequency) technology starts at approximately 30 kHz. The upper limit of radio technology is defined at 300 GHz (λ= 1mm) .

If the wavelength is sufficiently small, electrons split off, which ionize the atom. This border for ionization is indistinct as a function of the atomic structure and lies between 300 nm and 30 nm. As agreed, it is however specified at a wavelength of 100 nm, therefore this is where the UV range ends. The most important atoms C, O and N are not yet ionizable. However, this does not apply to larger molecular structures.

The transition from the x-ray to the γ-ray is considered to be about 10 EHz (1019 Hz), and there also exists a large range of overlap here.

The following will provide a short overview of the applications and the occurrence of electromagnetic processes at different frequencies. As we can see from these examples, electromagnetic processes can be found everywhere in our daily lives. These run the spectrum over 24 orders of magnitude from a human heartbeat to cosmic radiation and are usually not perceived by most people as being different forms of the same phenomenon.


Frequency [Hz] Application/occurrence
approx. 1 The human heartbeat at rest
5 ... 15 Brain currents

Basic frequency of sferics

8 ... 10 Underwater signaling
16.666 Railway current power frequency
60 Household current power frequency (North America)
3103 Analog telephone signal bandwidth
30 ... 300103 Long waves
0.3 ... 3106 Medium waves
3 ... 30106 Short waves
30 ... 300106 USW, VHF
0.3 ... 3109 UHF
0.5 ... 4109 Computer clock rate
1 ... 50109 Radar
4.6 ... 7.51014 Visible light
1016 ... 1020 X-rays
1020 ... 1024 Gamma radiation
> 1024 Cosmic radiation

Typical high-frequency applications are radio relay systems, radar installations, mobile radio, satellite and television engineering, radio, medical apparatus and many more. However, even computers with high-frequency clock rates must be included in this domain. Radio waves bearing the abbreviations LW (long wave), MW (medium wave), SW (short wave) and USW (ultrashort wave) are generally well-known. Television frequencies are labeled VHF (very high frequency) and UHF (ultra high frequency). The range from 500 MHz to 5 GHz is of particular interest for modern living since all important communications services are found within this range.

This section of the frequency band from 500 MHz to 5 GHz represented in logarithmic scale shows the most important applications. The proposed UMTS (Universal Mobile Telecommunications System) mobile radio standard of approximately 2 GHz and the HiperLAN system (High Performance Local Area Networks) 5.2 GHz for the transmission of high data rates are the wave of the future.


Microwave ovens at 2.4 GHz, satellite installations at 11 GHz, visible light at approximately 600 THz, images produced by x-rays at 1019 Hz, radioactivity of ceramic tiles and cosmic radiation beyond 1024 Hz are other phenomena, all of which are based on electromagnetic processes. If we usually speak almost exclusively of waves when discussing in lower frequencies, it is usually easier to understand and more common to speak of high frequency cosmic radiation in terms of particles based on wave-particle duality.

We must also include the infrared radiation of the human body and other electromagnetic processes such as the DC magnetic field and the earth's magnetic field all of which play an almost unconscious role in everyday life. Furthermore, the questions concerning light in general, colors, the dominance of blue and green in nature, the color of blood, etc. must also be considered.


Last Update: 2010-12-01