|
Photophone Plaque (no Copyright Applies)
The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell. On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft.) away.Carson 2007, pg. 76–78Mims 1982, p. 11. Bell believed the photophone was his most important invention. Of the 18 patents granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention haveever made, greater than the teleph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photophone Plaque (no Copyright Applies)
The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell. On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft.) away.Carson 2007, pg. 76–78Mims 1982, p. 11. Bell believed the photophone was his most important invention. Of the 18 patents granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention haveever made, greater than the teleph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoacoustic Effect
The photoacoustic effect or optoacoustic effect is the formation of sound waves following light absorption in a material sample. In order to obtain this effect the light intensity must vary, either periodically (''modulated light'') or as a single flash (''pulsed light'').Rosencwaig, A. (1980''Photoacoustics and photoacoustic spectroscopy'' Chemical Analysis: a Series of Monographs on Analytical Chemistry and Its Applications, Vol. 57. New York:John Wiley & Sons, . The photoacoustic effect is quantified by measuring the formed sound (pressure changes) with appropriate detectors, such as microphones or piezoelectric sensors. The time variation of the electric output (current or voltage) from these detectors is the photoacoustic signal. These measurements are useful to determine certain properties of the studied sample. For example, in photoacoustic spectroscopy, the photoacoustic signal is used to obtain the actual absorption of light in either opaque or transparent objects. It is u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mabel Gardiner Hubbard
Mabel Gardiner Hubbard (November 25, 1857 – January 3, 1923) was an American businesswoman, and the daughter of Boston lawyer Gardiner Green Hubbard. As the wife of Alexander Graham Bell, inventor of the first practical telephone, she took the married name Mabel Bell.Eber, Dorothy HarleyHubbard, Mabel Gardiner (Bell) in ''Dictionary of Canadian Biography'', Vol. 15, University of Toronto/Université Laval, 2003, accessed August 8, 2013.Toward, 1984. From the time of Mabel's courtship with Graham Bell in 1873, until his death in 1922, Mabel became and remained the most significant influence in his life.Winefield, RichardNever the Twain Shall Meet: Bell, Gallaudet, and the Communications Debate Gallaudet University Press, 1987, pp.72–77, , . Folklore held that Bell undertook telecommunication experiments in an attempt to restore her hearing which had been destroyed by disease close to her fifth birthday, leaving her completely deaf for the remainder of her life. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photophone Receiver 4074172975 288f2808f0 O
The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell. On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft.) away.Carson 2007, pg. 76–78Mims 1982, p. 11. Bell believed the photophone was his most important invention. Of the 18 patents granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention haveever made, greater than the teleph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photophone Transmitter 4074931746 9f996df841 B
The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell. On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft.) away.Carson 2007, pg. 76–78Mims 1982, p. 11. Bell believed the photophone was his most important invention. Of the 18 patents granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention haveever made, greater than the teleph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Wave
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (shorter than a grain of rice); at 30 Hz the corresponding wavelength is (longer than the radius of the Earth). Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects. Radio waves are generated artificially by an electronic device called a transmitter, which is connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver, which p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiophone
A radiotelephone (or radiophone), abbreviated RT, is a radio communication system for conducting a conversation; radiotelephony means telephony by radio. It is in contrast to '' radiotelegraphy'', which is radio transmission of telegrams (messages), or ''television'', transmission of moving pictures and sound. The term is related to radio broadcasting, which transmit audio one way to listeners. Radiotelephony refers specifically to two-way radio systems for bidirectional person-to-person voice communication between separated users, such as CB radio or marine radio. In spite of the name, radiotelephony systems are not necessarily connected to or have anything to do with the telephone network, and in some radio services, including GMRS, interconnection is prohibited. Design Mode of emission The word ''phone'' has a long precedent beginning with early US wired voice systems. The term means ''voice'' as opposed to telegraph or Morse code. This would include systems fitting int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around 1 millimeter (300 GHz) to the nominal red edge of the visible spectrum, around 700 nanometers (430 THz). Longer IR wavelengths (30 μm-100 μm) are sometimes included as part of the terahertz radiation range. Almost all black-body radiation from objects near room temperature is at infrared wavelengths. As a form of electromagnetic radiation, IR propagates energy and momentum, exerts radiation pressure, and has properties corresponding to both those of a wave and of a particle, the photon. It was long known that fires emit invisible heat; in 1681 the pioneering experimenter Edme Mariotte showed that glass, though transparent to sunlight, obstructed radiant heat. In 1800 the astronomer Sir William Herschel discovered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiant Energy
Radiant may refer to: Computers, software, and video games * Radiant (software), a content management system * GtkRadiant, a level editor created by id Software for their games * Radiant AI, a technology developed by Bethesda Softworks for ''The Elder Scrolls'' games * Radiant, the team that opposes ''Dire'' on ''Dota 2'' Music * ''Radiant'' (Atlantic Starr album), 1981 * ''Radiant'' (Iris album), 2014 Ships * HMS ''Radiant'' (1916), a destroyer of the British Royal Navy launched in 1916 and sold in 1920 * USS ''Radiant'', the name of more than one United States Navy ship * ''Radiant'' (yacht), a 2009 Lürssen built yacht Others * Radiant heat, or thermal radiation, electromagnetic radiation emitted from the surface of an object which is due to the object's temperature * Radiant heating, a technology for heating indoor and outdoor areas * Radiant (Kitchen manufacturer), an Australian manufacturer of products for kitchens and laundries * Radiant (''Magic: The Gathering''), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electrical Resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm (), while electrical conductance is measured in siemens (S) (formerly called the 'mho' and then represented by ). The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance and low conductance, while objects made of electrical conductors like metals tend to have very low resistance and high conductance. This relationship is quantified by resistivity or conductivity. The nature of a material is not the only factor in resistance and conductance, however; it also depends on the size and shape of an object because these properties are extensive rather than intens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus (optics)
In geometrical optics, a focus, also called an image point, is a point where light rays originating from a point on the object converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the blur circle. This non-ideal focusing may be caused by aberrations of the imaging optics. In the absence of significant aberrations, the smallest possible blur circle is the Airy disc, which is caused by diffraction from the optical system's aperture. Aberrations tend to worsen as the aperture diameter increases, while the Airy circle is smallest for large apertures. An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, and out of focus if light is not well converged. The border between these is sometimes defined using a "circle of confusion" criterion. A principal focus or focal point is a special focus: * For a lens, or a spherical or parabolic mirror, it is a point ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Photophone Plaque (no Copyright Applies)")
