![]() The two oscillating energy fields are mutually perpendicular (illustrated in Figure 2) and vibrate in phase following the mathematical form of a sine wave. From these observations, he concluded that visible light was a form of electromagnetic radiation.Īn electromagnetic wave travels or propagates in a direction that is oriented at right angles to the vibrations of both the electric ( E) and magnetic ( B) oscillating field vectors, transporting energy from the radiation source to an undetermined final destination. Maxwell speculated that the two phenomena were so closely bound that they often acted together as electromagnetism, and discovered that alternating current would produce waves composed of both entities that radiated out into space at the speed of light. During the next few decades, additional investigations following these leads produced an increasing amount of evidence that electricity and magnetism were very closely related to each other.įinally, in 1865, Scottish scientist James Clerk Maxwell expanded his kinetic theory of gases to mathematically explain the links between electricity and magnetism. Later that same year, French scientist André-Marie Ampère demonstrated that two wires carrying electrical currents could be made to attract or repel each other, in a fashion similar to that of magnetic poles. Start Tutorial »Įlectricity and magnetism were first associated in 1820 when Danish physicist Hans Christian Oersted discovered that electrical current flowing through a wire could produce deflections of a compass needle. ![]() Interact with the tutorial to vary the wavelength and the fill factor of electric and magnetic field vectors. By observing the rate at which various colors of light stimulate darkening of paper saturated with a solution of silver nitrate, Ritter discovered that another invisible form of light, beyond the blue end of the spectrum, yielded the fastest rates.Įxplore wave propagation through space with a sinusoidal representation of electromagnetic radiation. Ultraviolet radiation, at the other end of the visible spectrum, was discovered by Wilhelm Ritter, who was one of the first scientists to investigate the energy associated with visible light. Herschel suggested that there must be another type of light in this region that is not visible to the naked eye. British scientist and astronomer William Herschel was investigating the association between heat and light with a thermometer and a prism when he found that the temperature was highest in the region just beyond the red portion of the visible light spectrum. Infrared light, which lies beyond the longer red wavelengths of visible light, was the first "invisible" form of electromagnetic radiation to be discovered. The link between light, electricity, and magnetism was not immediately obvious to early scientists who were experimenting with the fundamental properties of light and matter. ![]() Visible light represents only a small portion of the entire spectrum of electromagnetic radiation (as categorized in Figure 1), which extends from high-frequency cosmic and gamma rays through X-rays, ultraviolet light, infrared radiation, and microwaves, down to very low frequency long-wavelength radio waves. The term electromagnetic radiation, coined by Sir James Clerk Maxwell, is derived from the characteristic electric and magnetic properties common to all forms of this wave-like energy, as manifested by the generation of both electrical and magnetic oscillating fields as the waves propagate through space. The mechanisms by which visible light is emitted or absorbed by substances, and how it predictably reacts under varying conditions as it travels through space and the atmosphere, form the basis of the existence of color in our universe. Electromagnetic radiation, the larger family of wave-like phenomena to which visible light belongs (also known as radiant energy), is the primary vehicle transporting energy through the vast reaches of the universe. Visible light is a complex phenomenon that is classically explained with a simple model based on propagating rays and wavefronts, a concept first proposed in the late 1600s by Dutch physicist Christiaan Huygens.
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