Electromagnetic (EM) radiation is a form of power that is all around us and also takes numerous forms, such as radio waves, microwaves, X-rays and gamma rays. Sunshine is also a type of EM energy, however visible irradiate is just a small section of the EM spectrum, which contains a broad range of electromagnetic wavelengths.

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Electromagnetic theory

Electricity and magnetism were once thought to be different forces. However, in 1873, Scottish physicist James salesperson Maxwell emerged a unified theory of electromagnetism. The examine of electromagnetism deals with how electrically charged particles communicate with every other and with magnetic fields.

There are four main electromagnetic interactions:

The force of attraction or repulsion in between electric fees is inversely proportional come the square the the distance in between them.Magnetic poles come in pairs the attract and repel every other, lot as electric charges do.An electric current in a wire produces a magnetic field whose direction counts on the direction that the current.A moving electrical field to produce a magnetic field, and also vice versa.

Maxwell also developed a set of formulas, referred to as Maxwell"s equations, to define these phenomena.

Waves and also fields

EM radiation is created when an atom particle, such as an electron, is increased by an electric field, leading to it come move. The motion produces oscillating electric and magnetic fields, which travel at ideal angles to each other in a bundle of irradiate energy dubbed a photon. Photons travel in harmonic tide at the faster speed feasible in the universe: 186,282 mile per second (299,792,458 meters per second) in a vacuum, additionally known as the rate of light. The tide have certain characteristics, offered as frequency, wavelength or energy.

Electromagnetic waves are formed when an electric field (shown in red arrows) couples with a magnetic field (shown in blue arrows). Magnetic and electric areas of an electromagnetic wave are perpendicular to every other and to the direction that the wave. (Image credit: NOAA.)

A wavelength is the distance between two continually peaks of a wave. This distance is given in meters (m) or fractions thereof. Frequency is the number of waves that form in a given length the time. The is generally measured together the number of wave cycles per second, or hertz (Hz). A brief wavelength way that the frequency will be higher because one cycle have the right to pass in a much shorter amount that time, according to theUniversity the Wisconsin. Similarly, a much longer wavelength has actually a lower frequency because each bike takes much longer to complete.

The EM spectrum

EM radiation spans one enormous variety of wavelengths and frequencies. This selection is well-known as the electromagnetic spectrum. The EM spectrum is generally separated into 7 regions, in stimulate of decreasing wavelength and increasing energy and also frequency. The common designations are: radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma rays. Typically, lower-energy radiation, such together radio waves, is expressed together frequency; microwaves, infrared, visible and also UV light are usually expressed together wavelength; and also higher-energy radiation, such together X-rays and gamma rays, is expressed in terms of power per photon.

The electromagnetic spectrum is generally divided into 7 regions, in stimulate of to decrease wavelength and also increasing energy and also frequency: radio waves, microwaves, infrared, clearly shows light, ultraviolet, X-rays and also gamma rays. (Image credit: Biro Emoke Shutterstock)

Radio waves

Radio waves are at the lowest range of the EM spectrum, v frequencies of increase to around 30 billion hertz, or 30 gigahertz (GHz), and wavelengths higher than about 10 millimeter (0.4 inches). Radio is used mainly for interactions including voice, data and also entertainment media.


Microwaves autumn in the selection of the EM spectrum between radio and IR. They have frequencies from about 3 GHz up to about 30 sunshine hertz, or 30 terahertz (THz), and wavelengths of about 10 mm (0.4 inches) to 100 micrometers (μm), or 0.004 inches. Microwaves are supplied for high-bandwidth communications, radar and as a heat resource for microwave ovens and also industrial applications.


Infrared is in the variety of the EM spectrum between microwaves and also visible light. IR has actually frequencies from around 30 THz up to about 400 THz and wavelengths of about 100 μm (0.004 inches) come 740 nanometers (nm), or 0.00003 inches. IR light is invisible to human eyes, but we have the right to feel the as heat if the soot is sufficient.

clearly shows light

Visible irradiate is discovered in the center of the EM spectrum, between IR and UV. It has actually frequencies of around 400 THz to 800 THz and wavelengths of about 740 nm (0.00003 inches) come 380 nm (.000015 inches). More generally, visible irradiate is characterized as the wavelength that room visible to most human eyes.


Ultraviolet light is in the selection of the EM spectrum in between visible light and also X-rays. It has actually frequencies of about 8 × 1014to 3 × 1016Hz and also wavelengths of around 380 nm (.000015 inches) to about 10 nm (0.0000004 inches). UV irradiate is a ingredient of sunlight; however, that is invisible to the human being eye. The has numerous medical and industrial applications, but it can damages living tissue.


X-rays are approximately classified right into two types: soft X-rays and also hard X-rays. Soft X-rays comprise the range of the EM spectrum between UV and gamma rays. Soft X-rays have frequencies of about 3 × 1016to around 1018Hz and also wavelengths of around 10 nm (4 × 10−7inches) to around 100 picometers (pm), or 4 × 10−8inches. Tough X-rays occupy the same an ar of the EM spectrum together gamma rays. The just difference in between them is their source: X-rays are produced by accelerating electrons, when gamma rays are developed by atomic nuclei.

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Gamma-rays room in the variety of the spectrum above soft X-rays. Gamma-rays have frequencies better than about 1018Hz and wavelengths of less than 100 afternoon (4 × 10−9inches). Gamma radiation causes damage to living tissue, which provides it valuable for killing cancer cells when applied in closely measured doses to tiny regions. Uncontrolled exposure, though, is incredibly dangerous come humans.