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Electromagnetic Waves Definition
Electromagnetic radiation involves electromagnetic waves, which are coordinated oscillations of both electric and magnetic fields. It can further be said that electromagnetic waves are the composition of oscillating electric and magnetic fields.
Electromagnetic radiation or electromagnetic waves are produced due to periodic change of electric or magnetic field. In a vacuum or void, electromagnetic waves generally travel with the speed of light which is represented as c.
1. The position of an electromagnetic waves present within the electromagnetic spectrum can be categorized by its frequency of oscillation or wavelength.
2. Some sources of electromagnet radiation include; the cosmos (for instance – the sun and stars), radioactive elements, and manufactured devices.
3. EM displays a dual wave and particle nature.
What is Electromagnetic Waves?
Electromagnetic radiations are produced when an atomic particle, such as an electron, is accelerated and is moved by an electric field. This movement produces oscillating electric and magnetic fields, which are at right angles or 90 degrees to each other and usually travel in a bundle of light energy termed as photons.
A wavelength is defined as the distance between two consecutive troughs (peak) of a wave. This distance is commonly measured in meters (m).
Frequency is referred to as the number of waves formed in a given period of time. It is generally measured in hertz (Hz).
Mathematical Representation of Electromagnetic Wave
In the electromagnetic wave, E is referred to as the electric field vector and B is defined as the magnetic field vector.
Therefore, the direction of propagation of the electromagnetic wave is thus given by vector cross product of the electric field and magnetic field. It is shown below: E→×B→
Graphical Representation of Electromagnetic Waves
Electromagnetic waves are commonly shown by a sinusoidal graph. It comprises of time-varying electric and magnetic fields which are perpendicular or at right angles to each other and are also perpendicular (right angles) to the direction of propagation of waves. The uppermost point of the wave is named as crest whereas the lowest point is termed as a trough. The waves travel at a fixed velocity of 3 x 108 m.s-1 in vacuum.
The Electromagnetic Spectrum
EM radiation spans a widespread range of wavelengths and frequencies. This range is termed as the electromagnetic spectrum. The EM spectrum is usually divided into seven regions, based on decreasing wavelength and increasing energy and frequency. The common terms are: radio waves, microwaves, infrared (IR), ultraviolet (UV), X-rays, gamma rays and visible light. Normally, lower-energy radiation such as radio waves, is represented in frequency and microwaves, infrared, visible and UV light are generally expressed as wavelength and higher-energy radiation, like X-rays and gamma rays are stated in energy per photon.
Radio waves has the lowest range of the EM spectrum, with frequencies equal to 30 gigahertz (GHz), and wavelengths of 10 millimetres or 0.4 inches.
Uses: Radio waves are used mainly for communications including voice, data, and entertainment media.
Microwaves lie in between the EM spectrum of radio and infrared waves. They have frequencies from about 3 GHz up to about 30 trillion hertz, or 30 terahertz (THz), and wavelengths of 10 mm (0.4 inches) to 100 micrometres (μm) or 0.004 inches.
Uses: Microwaves are commonly used for high-bandwidth communications, radar and is also used as a heat source for microwave ovens and industrial applications.
Infrared is in the range of the EM spectrum that lies between microwaves and visible light. IR express frequencies from 30 THz up to about 400 THz and wavelengths of about 100 μm (0.004 inches) to 740 nanometres (nm), or 0.00003 inches.
Uses: IR light is generally invisible to naked eyes, but if the intensity is enough, then it can be felt as heat.
Visible light lies in the middle of the infrared and ultraviolet waves of EM spectrum. It displays the frequencies of around 400 THz to 800 THz and wavelengths of nearly 740 nm (0.00003 inches) to 380 nm (.000015 inches).
Uses: visible light can be referred to as the wavelengths which are visible to naked eyes.
Ultraviolet light lies in the range of the EM spectrum between visible light and X-rays. Its frequencies are around 8 × 1014 to 3 × 1016 Hz and wavelengths of about 380 nm (.000015 inches) to about 10 nm (0.0000004 inches).
Uses: UV light is referred to as a constituent of sunlight; though, it is not visible to the naked eye. These radiations further have several medical and industrial applications.
• These rays are germicidal in nature, kills bacteria, viruses and moulds present in the air, water and on surfaces.
• It is also used to spot phony bank notes, as these fakes notes turn fluorescent in colour under UV light whereas real notes don’t turn fluorescent under the UV light.
X-rays are widely classified into two types, soft X-rays, and hard X-rays. Soft X-rays have the range that lie between UV and gamma rays. Soft X-rays have frequencies of about 3 × 1016 to 1018 Hz and wavelengths of about 10 nm (4 × 10−7 inches) to 100 picometers (pm), or 4 × 10−8 inches. Hard X-rays further reside in the same region of the EM spectrum as gamma rays. The only difference between them is; X-rays are produced by accelerating electrons, whereas gamma rays are formed by nuclei of atom.
Uses: The most vital use of X-rays is that it is used to detect bone fracture.
Gamma-rays generally have frequencies greater than 1018 Hz and wavelengths less than 100 pm (4 × 10−9 inches).
Uses: Gamma radiation damage the living cells and tissues, which is beneficial for killing of cancer cells in small doses. But it is tremendously hazardous to humans in uncontrolled amount.
Electromagnetic Waves Citations
- Benefits and hazards of electromagnetic waves, telecommunication, physical and biomedical: a review. Eur Rev Med Pharmacol Sci . 2019 Apr;23(7):3121-3128.
- Electromagnetic radiation. Br Med Bull . 2003;68:157-65.
- Effect of electromagnetic waves on human reproduction. Ann Agric Environ Med . 2017 Mar 31;24(1):13-18.