According to classical physics, electromagnetic radiation is energy transmitted at the speed of light through oscillating electric and magnetic fields or electromagnetic waves. Also, according to quantum physics, it is described as the wave or flow of photons of the electromagnetic field that propagate or radiate through space or a physical medium, carrying electromagnetic radiant energy.
A More Basic Description and Definition of Electromagnetic Radiation
Simplified Description and Definition
Some people might still have a hard time grasping the description and definition of electromagnetic radiation or EM radiation. Nevertheless, for the sake of simplicity, it can also be described as a stream of mass-less particles called photons. Each of these photons travels through space or a material medium in a wave-like pattern at the speed of light.
Each photon carries a specific amount of energy. EM radiation is fundamentally made up of these small particles, and an electromagnetic wave represents the stream of these particles. Sometimes referred to as a quantum of electromagnetic energy, a particular photon can also be described as a little packet of energy.
Photons and Wave-Particle Properties
Take note that photons are also elementary particles and as such, they have no substructure. Furthermore, remember that they have no mass. A specific photon has energy and movement, but it does not have mass or electrical charge.
Photons also have the properties of waves and some of the properties of other subatomic particles. Hence, the characteristics of these mass-less particles also describe the fundamental nature and properties of electromagnetic radiation.
A more specific description of the property of EM radiation is that it exhibits both wave properties and particle properties. This is a testament to the concept of wave-particle duality in quantum mechanics. The visible light, one of the different types of EM radiation, also exhibits both wave and particle properties.
Abundance, Sources, and Different Types of Electromagnetic Radiation
Natural and Artificial Sources
Electromagnetic radiation is almost everywhere. They come from natural sources such as the Sun and other stars, as well as other cosmic objects and events including the regions around black holes and explosions of a supernova. They also come from radioactive elements such as radon, radium, uranium, and thorium, among others.
Humankind has also developed technologies for creating EM radiation. Examples of applications include household fixtures such as LED and fluorescent lamps, microwave ovens, and television. Medical imaging equipment also use specific types of electromagnetic radiation. Scientists have also created artificial radioactive elements that emit EM radiation.
Types of Electromagnetic Radiation
Understanding and appreciating further what electromagnetic radiation is would require understanding the electromagnetic spectrum. Thus, by definition, the EM spectrum represents that different types of EM radiation and their frequencies. It is specifically the range of frequencies of EM radiation and their corresponding wavelengths and photon energy.
The different types of electromagnetic radiation or different electromagnetic waves are essentially categorized according to their frequencies, as well as their wavelength and photon energy. Take note of the following:
1. Radio Waves: Placed on the most-left part of the EM spectrum, they have frequencies ranging from 3 Hz to 30 GHz, as well as wavelengths of 100000 km to 30 cm. They have the longest wavelengths of all the electromagnetic waves. Natural sources include lightning and astronomical objects.
Humankind has used radio waves in wireless communication technology to include radio communication using broadcast systems and mobile telephony, wireless Internet and local wireless networking, radar detection system, and communications satellite, and radio navigation.
2. Microwaves: EM radiation with frequencies ranging from 3 Hz to 300 GHz in the electromagnetic spectrum are generally classified as radio waves. However, frequencies between 300 MHz and 300 GHz or those falling under the very high frequency and extreme high-frequency range are technically classified as microwaves. They are essentially radio waves with higher frequencies.
Specific applications include wireless short-distance communication to include wireless LAN protocol via Wi-Fi and Bluetooth technologies, and mobile telephony standards to include the GSM, 3G, 4G and LTE, and 5G standards. Other applications include wireless power transfer and heating as demonstrated by microwave ovens, solar power satellite systems, and reactive ion etching, among others.
3. Infrared: Next to radio waves and wavelengths and before the visible light spectrum are infrared radiation or infrared light. They have wavelengths ranging from 700 nm to 1 mm and frequencies from 430 THz to 300 GHz. Furthermore, they are also categorized into two subtypes: near-infrared and far-infrared.
Some of the common applications of near IR radiation include use in IR communication and remote control technology for controlling televises and other devices, in medical and agricultural imaging using near IR spectroscopy, and in fiber optic communication. Applications of far IR radiation include thermal scanning and imaging, as well as in specific non-abrasive medical treatments based on radiotherapy.
4. Visible Light: The light coming from the rays of the sun and produced by light bulbs such as fluorescent and light-emitting diode lamps represents another type of electromagnetic radiation. Hence, the visible light spectrum represents all EM radiation that can be seen by the human eye. They have wavelengths ranging from 400 nm to 700 nm and frequencies of roughly 430 THz to 750 THz.
The properties of visible light are frequency, wavelength, and intensity. Within the specific spectrum, humans perceive light with different frequencies, wavelengths, and intensities based on the following colors: red, orange, yellow, green, blue, indigo, and violet. Of course, a typical light would appear white but when it passes through a prism or similar material with prism-like properties, it separates into individual bands. The best natural example is a rainbow.
5. Ultraviolet Radiation: Most of the ultraviolet radiation on Earth comes from the Sun. It represents EM radiation with wavelengths between 10nm and 400nm, and frequencies between 30 PHz and 750 THz. There are also specific subtypes of UV radiation: UVA, UVB, and UVC rays. Only UVA and UVB pass through the atmosphere.
Overexposure to sunlight is harmful to the skin and overall health because of the adverse effect of UV radiation. UVA rays and UVB rays have different effects: the latter can cause sunburn and can result in direct DNA and RNA damage while the former has been linked to photoaging and indirect damage to DNA and RNA. These harmful effects necessitate the use of sunscreens with broad-spectrum protection, wearing protective clothing, and minimizing exposure to sunlight.
6. X-Radiation or X-Rays: Next to ultraviolet radiation in the electromagnetic spectrum are x-rays or x-radiation. They are high-energy EM radiation that can penetrate a number of objects, including human tissue. Their wavelengths range from 10 pm to 10 nm and their frequencies are between 30 PHz and 30 AHz.
This type of EM radiation has seen wide application in medical imaging technologies such as projectional radiography, computed tomography, and fluoroscopy. Because they are a form of ionizing radiation, they are also used in a specific medical treatment called radiation therapy to target and kill malignant tissues and cells.
7. Gamma Rays: At the end of the electromagnetic spectrum are gamma rays. They have the shortest wavelengths and highest frequencies within the spectrum. Furthermore, they are a specific form of ionizing and penetrating EM radiation emerging from the radioactive decay of atomic nuclei. Other sources include thunderstorms, solar flares, cosmic rays, pulsars and magnetars, active galaxies, and quasars.
Note that gamma rays and x-rays overlap in the EM spectrum. The use of these two terminologies tends to differ between scientific disciplines. Nevertheless, because they are ionizing radiation similar to extreme UV, soft x-rays, and hard x-rays, they are biologically hazardous. Exposure to gamma rays can result in organ damage.
