This is such a basic technology that we take it almost for granted, but if you delve into the quantum physics behind it, you find that something amazing is happening.
Two Point Source Interference
The operating principle behind the light bulb is very simple: you run an electric current through a thin filament, which causes it to get hot. Hot objects emit light, so the bulb glows. The high temperature is the reason for the bulb-- heating a filament to the necessary temperatures in air will cause chemical reactions that quickly destroy the filament. This can be avoided by putting the filament in a glass bulb with the air either pumped away or, in higher-wattage bulbs, replaced with an inert gas like argon.
Max Planck in photo from Wikimedia next to n incandescent bulb and its spectrum. Image by Chad Orzel. The color of the light does not depend strongly on the properties of the material being heated, just its temperature, and the spectrum of light-- the intensity of the light emitted at various wavelengths-- takes the form of a broad peak whose wavelength changes location in a fairly simple way.
You can see an example of this shape in this famous xkcd cartoon. This spectrum turns out to be surprisingly difficult to explain, though. Max Planck was able to explain the spectrum in , but he had to resort to a desperate mathematical trick, assigning a characteristic energy to the light-emitting material that depended on the frequency of the light.
This is the idea Einstein picked up in , introducing what we now call photons in order to explain the photoelectric effect. And these models led inevitably to the development of quantum mechanics, in all its glory. So the fact that an incandescent light bulb glows is directly dependent on the particle nature of light, and the wave nature of matter.
That by itself is enough to add some wonder to the operation of an old-school light bulb. A much more obviously quantum sort of system is the emission of light from individual atoms-- from the 's on it was known that atoms of particular elements absorb and emit light at very well-defined wavelengths. This was used to determine the elemental composition of various types of stars, and even to discover new elements-- the element helium, favorite of toddlers who love balloons, is named after the sun god Helios, because it was first discovered thanks to an unexplained absorption line in the spectrum of the Sun.
Example spectra from various types of stars, showing the dark absorption lines that astronomers use to determine their composition.
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Turn on the current instantly! But the dynamo needed time to build its current, and Kemmler wheezed and gasped before the horrified witnesses as the electricity began to course through his body.
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Some witnesses fainted while others vomited, as it appeared that Kemmler was on the verge of regaining consciousness. The back of his coat briefly caught fire. Minutes passed until Kemmler finally went rigid. The current stopped and he was pronounced dead by Dr. The elephant had killed three men in recent years—one a trainer who had tried to feed Topsy a lit cigarette. Edison had Topsy fitted with copper-wire sandals , and before a crowd of thousands, an AC current of 6, volts was sent coursing through the elephant until she toppled to her side, dead.
The inventors’ battle over the delivery of electricity was an epic power play
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The Surprisingly Complicated Physics Of A Light Bulb
For additional information, see the Global Shipping Program terms and conditions - opens in a new window or tab No additional import charges on delivery Delivery: Estimated between Wed. Includes international tracking Payments: Special financing available. An error occurred, please try again. Brand New: A new, unread, unused book in perfect condition with no missing or damaged pages. From Darkness To Light is a gripping tale of the events surrounding the invention of the electric light by Thomas A.
Edison and the plot to sabotage the invention.
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