Radiant Energy


All objects give off energy in the form of electromagnetic radiation.


For instance, the heat that we feel from fire or the sun is a form of electromagnetic radiation. Any object that has a temperature gives off this form of energy which is infrared radiation.  It does not require a medium to travel through; it can travel through a vacuum.  If an object is heated to a high enough temperature, it will glow with visible light, which is of higher energy than infrared radiation.


Objects that transmit low energy radiation will produce electromagnetic radiation with long wavelengths and low frequencies.  Objects that transmit radiation with a high energy will produce waves with short wavelengths and high frequencies.  The electromagnetic spectrum is shown below, showing the relative wavelengths and frequencies for the different named types of radiation. 




Electromagnetic waves are essentially all alike, the only difference being the wavelength.  All electromagnetic radiation consists of an electric field and a magnetic field which are at right angles to each other.







How Are Electromagnetic Waves Produced?







A charged particle, such as a proton or an electron produces an electric field.  This electric field is either directed towards the negative particle or away from the positive particle.  The electric field is multi-directional.  When the electric field consisting of a charged particle moves through a wire, such as in a circuit, a magnetic field is produced at right angles to the electric field. The magnetic field is “wrapped” around the wire.  This is the principle behind an electromagnet.  Electric fields and magnetic fields influence each other.  If you move a magnet along a wire, you influence the movement of charged particles and so produce an electric field.    Electromagnetic radiation, which consists of both electric and magnetic components, is produced when a charged particle accelerates.  The charge produces the electric component and the movement of the charge creates the magnetic component.  Since the particle is accelerating, (moving faster, slower or changing direction), these electric and magnetic fields are constantly in flux, they form and disappear over and over.  This pattern of repeated formation of the fields is the origin of the wave propagation.