Electromagnetic radiation (EM radiation or EMR) is a form of radiant energy released by certain electromagnetic processes. Visible light is one type of electromagnetic radiation, and in some contexts light can refer to all EMR. Other familiar forms are invisible electromagnetic radiations such as X-rays and radio waves. EMR consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light. The oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave. Electromagnetic waves can be characterized by either the frequency or wavelength of their oscillations to form the electromagnetic spectrum, which includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Electromagnetic waves are produced whenever charged particles are accelerated, and these waves can subsequently interact with any charged particles. EM waves carry energy, momentum and angular momentum away from their source particle and can impart those quantities to matter with which they interact. EM waves are massless, but they are still affected by gravity. Electromagnetic radiation is associated with those EM waves that are free to propagate themselves ("radiate") without the continuing influence of the moving charges that produced them, because they have achieved sufficient distance from those charges. Thus, EMR is sometimes referred to as the far field. In this jargon, the near field refers to EM fields near the charges and current that directly produced them, as (for example) with simple magnets, electromagnetic induction and static electricity phenomena.
Accelerating Charges Emit Electromagnetic Waves
introduction to electromagnetic spectrum
Electromagnetic spectrum
Visualizing the waves
Radio Waves
How Radio Waves are Produced
Polarization of Waves
Doppler Effect
Applications of Doppler effect
Maxwell's Equation
Fresnel Equation
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