What is Electromagnetic Radiation?

Electromagnetic radiation is found everywhere in the Universe; it is an integral part of technology these days. Being a boon and a bane at the same time, it has been a subject of research since ages. Here's more...
Everything that we witness through our eyes is, in some way or the other, a manifestation of energy. Energy is the very essence of the universe and life. Though the term 'radiation' has a very simple meaning, it has significant usage and effect in the world of physics. Radiation in physics stands for a phenomenon in which energetic particles or waves travel through a medium. Correlating this to Electromagnetic Radiation (EMR), we can say that it is nothing but energy particles or waves that travel through a medium having the following properties:
  • EMR consists of electric and magnetic waves oscillating in a phase perpendicular to each other, as well as perpendicular to the direction of energy propagation.
  • EMR possesses both wave and particle-like characteristics.
The origin and theory of electromagnetic waves can be mostly credited to James Clark Maxwell, a Scottish physicist, and Heinrich Hertz, a German physicist.

Is Sunlight Electromagnetic Radiation?
After in-depth research and studies, Maxwell and Heinrich Hertz confirmed that electromagnetic waves (EMs) consisted of both magnetic and electrical components. Maxwell also calculated the speed of EM waves and found that they were equal to speed of light, thereby proving that even light is a form of EM. Further, it was found that sunlight consisted of a series of visible range of waves in the electromagnetic spectrum known as 'VIBGYOR'. Moreover, it was also found that sunlight consisted of some invisible electromagnetic streams, like ultraviolet rays, that were not visible to the naked eye, and were harmful, causing sunburn and cancer.

Range of EMRs
Our eyes and brain can only identify the visible part of the electromagnetic spectrum. Most of the wavelengths in EMRs are not sensed by us. The table below provides information about the numerous electromagnetic radiations and their range of wavelengths and frequency. Remember that wavelength and frequency are two of the most important parameters that determine the property of waves. Here are some important points you may find useful in your study of the table below.
  • One meter = 1000 millimeters
  • 1000 millimeters (mm) = 1 micron
  • 1 micron = 1000 nanometers (nm)
  • Wavelength is inversely proportional to frequency. Higher the frequency, lower is the wavelength and vice versa.
  • Frequency is the rate, or you can call it the speed, of the wave. It is measured in Hertz. The number of times a wave passes a given point per second is known as its frequency.
  • Wavelength is measured in micrometer, nanometer, and angstrom, and is the measure of distance between two successive crests or troughs of a wave.
  • Higher the frequency of a wave, more powerful is its nature to penetrate. In the table below, make a note of the point that frequencies for gamma and x-rays are very high and hence, they have great penetrative power.
Gamma raysAstrophysical process, radioactive decay1019 Hz & above0.03 to 0.003 nm
X - RaysDiagnostic radiography, X-Ray tubes, Computer tomography, celestial bodies1016 to 1019 Hz & above0.03 to 10 nm
Ultraviolet wavesSun, ultraviolet fluorescent lamps, UV LEDs, UV diodes & LASERs, gas discharge lamps1014 to 1016 Hz & above10 to 380 nm
Light wavesSun, luminous bodies, bulbs, lamps7.85 to 4.85 X 1014 Hz380 to 740 nm
Infra red wavesThermal efficiency analysis, remote temperature sensing, short-ranged wireless communication, spectroscopy, weather forecasting devices, infrared astronomy telescope and objects emitting thermal radiation at room temperature1 x 1012 to 4.3 x 1014 Hz750 nm to 3 microns
MicrowavesVacuum tubes, magnetron, klystron, Traveling-Wave Tube (TWT), and gyrotron, solid-state devices, field - effect transistors, Sun, telecommunication towers3 x 108 to 3 x 1011 Hz3 microns to 1 meter
Radio wavesTV station,astronomical sources, synchrotron radiation, transmitters3 x 104 to 3 x 108 Hz3 meters to 3 km

Going through this article, you must have got a few insights on electromagnetic radiation. Understand that electromagnetic radiation has both types of waves, ionizing and non-ionizing. Ultraviolet rays, gamma rays, and x-rays are ionizing, because they have the intensity and power to penetrate materials and break chemical bonds. The non-ionizing range of EMRs, that include near ultraviolet, visible light, infrared, microwave, radio waves, and low-frequency RF (longwave), are not strong enough to break chemical bonds or detach an electron from an atom. While ionizing radiation certainly has several health risks, even non-ionizing radiation is harmful in several ways.