What is Electromagnetic Radiation

Everything that we witness through our mortal eyes is in some or the other ways, a manifestation of energy. Energy is the essence of this Universe and life. The term 'radiation' although has a very simple meaning, it has significant usage and effect in the world of Physics. Radiation in Physics language 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 and they have the following properties:

• EMRs consist of electric and magnetic waves oscillating in phase perpendicular to each other as well as perpendicular to the direction of energy propagation.
• EMRs possess both wave and particle like characteristics.

So, did you understand what exactly is electromagnetic radiation? You can imagine EMRs to be waves or particles composed of electric and magnetic fields. Did you pay attention as to why I'm referring EMRs either as particles or waves? Well, that is due to the most famous wave-particle duality law in Physics. As per this law, matter exhibits both wave and particle like properties. Electromagnetic waves origin and theory are mostly credited to Scottish Physicist, James Clark Maxwell and the German Physicist, Heinrich Hertz.

Is Sunlight Electromagnetic Radiation?
After deep research and study when 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. So if you have been wondering 'what is the speed of electromagnetic radiation', then it is the same as the speed of light, that equals, 3.00 x 10⁸ ms^-1 approximately. Further, it was found that the sunlight consisted of series of visible range of waves in the electromagnetic spectrum known as 'VIBGYOR'. Moreover, it was also found that sunlight consists of some invisible electromagnetic streams like ultraviolet rays that are not visible to the naked eyes and are also harmful for health causing sun burns and cancer. Similarly, when you see a rainbow, it is the visible spectrum of sunlight that you're able to see!

Range of EMRs
Our eyes and brains can only identify visible part of electromagnetic spectrum. Most of the wavelengths in EMRs are not sensed by us. The light waves are sensed by eyes and brains while ultraviolet rays are not detected by our senses. The table below provides information about 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 to in your study of the table below.

• One meter = 1000 milimeters
• 1000 milimeters (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 to be 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, commonly for visible light spectrum. Wavelength is the measure of distance between two successive crests or troughs of 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 like gamma or x - rays are very high and hence, they've got great penetrative power.

Type	Sources	Frequency	Wavelength
Gamma rays	Astrophysical process, radioactive decay	1019 Hz & above	0.03 to 0.003 nm
X - Rays	Diagnostic radiography, X-Ray tubes, Computer tomography, celestial bodies	1016 to 1019 Hz & above	0.03 to 10 nm
Ultraviolet waves	Sun, ultraviolet fluorescent lamps, UV LEDs, UV diodes & LASERs, gas discharge lamps	1014 to 1016 Hz & above	10 to 380 nm
Light waves	Sun, luminous bodies, bulbs, lamps	7.85 to 4.85 X 1014 Hz	380 to 740 nm
Infra red waves	Thermal efficiency analysis, remote temperature sensing, short-ranged wireless communication, spectroscopy, weather forecasting devices, infrared astronomy telescope and objects emitting thermal radiation at room temperature	1 x 1012 to 4.3 x 1014 Hz	750 nm to 3 microns
Microwaves	Vacuum tubes, magnetron, klystron, Traveling-Wave Tube (TWT), and gyrotron, solid-state devices, field - effect transistors, Sun, telecommunication towers	3 x 108 to 3 x 1011 Hz	3 microns to 1 meter
Radio waves	TV station,astronomical sources, synchrotron radiation, transmitters	3 x 104 to 3 x 108Hz	3 meters to 3 km

By going through this article, you must have got insights on electromagnetic radiation. Understand that electromagnetic radiations have both types of waves, ionizing and non - ionizing. Ultraviolet rays, gamma rays and X - rays are ionizing radiations because they've got the intensity and power to penetrate in 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 radiations certainly have several health risks even the non - ionizing radiations are harmful in several ways.

Now that I have briefed you about general information on EMRs, I hope you must be able to understand the difference between radiation and electromagnetic radiation. You must now get back to your college library and continue to study more interesting books about EMRs and EMs. Remember to understand this topic well, as it has great application in every day life and higher physics.