Electromagnetic radiation refers to the transfer of all forms of radiation through space by electromagnetic waves. This includes gamma rays, ultraviolet (UV), infrared (IR), X-rays, and radio waves, as well as visible light.
- Detached from its source, electromagnetic radiation (EM radiation or EMR), is transported by electromagnetic waves (or their quanta, photons) and propagates through empty space at the speed of light.
- Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
- At the quantum scale of electromagnetism, electromagnetic radiation is described in terms of photons rather than waves. Photons are elementary particles responsible for all electromagnetic phenomena.
- The term quantum refers to the smallest quantity into which something can be divided. A quantum of a thing is indivisible into smaller units so they have no sub-structure. A photon is a quantum of electromagnetic radiation.
- A single photon with a wavelength corresponding with gamma rays might carry 100,000 times the energy of a single photon of visible light.
ABOUT LIGHT AS WAVES AND PARTICLES
- Electromagnetic radiation and the electromagnetic energy it transports can be described in terms of waves.
- Electromagnetic radiation (radiant energy) includes all wavelengths of light from radio waves to gamma rays.
- Electromagnetic radiation can be described in terms of photons and their properties.
- Energy: Photons have energy that depends on their frequency or wavelength. Higher-frequency photons have more energy than lower-frequency photons.
- Number: The number of photons in a given electromagnetic radiation depends on its intensity or brightness. Higher-intensity radiation has more photons than lower-intensity radiation.
- Direction: Photons travel in straight lines, but their direction can be changed by interacting with matter.
- Polarization: Photons can be polarized, which means that their electric and magnetic fields oscillate in a particular direction.
- Speed: Photons travel at the speed of light, which is approximately 299,792,458 meters per second in a vacuum.
About light, electromagnetic energy, electromagnetic radiation and radiant energy
There is a difference in meaning between the terms light, electromagnetic radiation, radiant energy and electromagnetic energy in physics.
- Light is best used to refer to the subset of electromagnetic radiation that is visible to the human eye, ranging from violet (shorter wavelengths) to red (longer wavelengths).
- Electromagnetic radiation refers to the transfer of all forms of electromagnetic radiation through space by electromagnetic waves and includes gamma rays, ultraviolet (UV), infrared (IR), X-rays, and radio waves, as well as visible light.
- Radiant energy is most commonly used to refer to electromagnetic radiation carried by electromagnetic waves. Radiant energy can be measured using instruments such as photometers, which detect the intensity of light or other forms of electromagnetic radiation.
- Electromagnetic energy is a more general term that refers to any form of energy that is carried by electromagnetic waves, including both radiant energy and other types of energy that are not radiant (e.g., static electric fields).
- The type of energy associated with electromagnetic radiation is a measurable quantity in physics, and its measurement is essential for understanding and analyzing physical systems and processes.
- The unit of measurement for electromagnetic energy in the International System of Units (SI) is the joule (J), which is defined as the amount of energy required to perform one joule of work
- The electronvolt (eV) is another unit of energy commonly used in atomic and subatomic physics.
Related diagrams
Each diagram below can be viewed on its own page with a full explanation.
Electromagnetic radiation is a type of energy more commonly simply called light. Detached from its source, it is transported by electromagnetic waves (or their quanta, photons) and propagates through space at the speed of light.
- Electromagnetic radiation (EM radiation or EMR) includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.
- Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
- At the quantum scale of electromagnetism, electromagnetic radiation is described in terms of photons rather than waves. Photons are elementary particles responsible for all electromagnetic phenomena.
- The term quantum refers to the smallest quantity into which something can be divided. A quantum of a thing is indivisible into smaller units so they have no sub-structure. A photon is a quantum of electromagnetic radiation.
- A single photon with a wavelength corresponding with gamma rays might carry 100,000 times the energy of a single photon of visible light.