Electromagnetic radiation (EMR) is a form of radiated or transported energy that does not require a medium in order to propagate, unlike mechanical waves such as sound and vibrations. Mechanical waves travel by transferring energy through molecular contact, causing molecules to bump into each other in order to transfer kinetic energy which can be observed visually in water ripples. Electromagnetic waves are created by magnetic and electric fields coupling together to form waves, usually released by certain electromagnetic processes. The most common examples of electromagnetic radiation are visible light and X-rays.
Electromagnetic radiation is also known as electromagnetic waves.
Electromagnetic radiation is energy emanated radially, formed through the combined vibration of electrical and magnetic fields. This type of energy does not require a medium in order to propagate, meaning that it can travel in the vacuum of space, unlike sound which requires matter such as air in order to propagate. The electric and magnetic fields that comprise an electromagnetic wave are perpendicular to each other in the direction that the wave is traveling, and it travels at the speed of light until it interacts with substantial matter or objects which may interfere with its propagation, such as concrete or metal.
Electromagnetic radiation or energy can be described through three properties:
- Energy — Describes the intensity of the EMR through electron volts, which is commonly used for energetic or active EMR, like gamma rays and X-rays.
- Wavelength — Describes the shape and movement of the wave and is a measure of the distance between repetitions of the shapes of the wave such as valleys, peaks and zero-crossings. This is one way of perceiving the wave through instruments and other sensors. For example, the visual characteristics of visible light such as color and visibility is dictated by the wavelength. The smallest wavelengths have been measured to be smaller than the size of an atom, while the largest are bigger than the diameter of our planet.
- Frequency — Describes the number of crests and falls or peaks and valleys that pass through a point in one second. The measurement unit for one cycle per second is the Hertz, after the man that established the existence of radio waves, Heinrich Hertz.
James Clerk Maxwell was the first scientist to postulate the existence of electromagnetic radiation/waves. He developed a scientific theory and equations to explain electromagnetic radiation and then summarized the relationship between magnetism and electricity into what are known as the Maxwell equations. Heinrich Hertz later confirmed Maxwell's theories and then applied them to the reception and production of electromagnetic waves.
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