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Whispering-gallery waves, or whispering-gallery modes, are a type of wave that can travel around a concave surface. Originally discovered for sound waves in the whispering gallery of St Paul’s Cathedral, they can exist for light and for other waves, with important applications in nondestructive testing, lasing, cooling and sensing, as well as in astronomy. ==Introduction== ] Whispering-gallery waves were first explained for the case of St Paul's Cathedral circa 1878〔(Rayleigh, Theory of Sound, vol. II, 1st edition, (London, MacMillan), 1878. )〕 by Lord Rayleigh, who revised a previous misconception〔(Tyndall, The Science of Sound (New York, Philosophical Library), 1867, p. 20. )〕〔(B. Airy, On Sound and Atmospheric Vibrations, with the Mathematical Elements of Music (London, MacMillan), 1871, p. 145. )〕 that whispers could be heard across the dome but not at any intermediate position. He explained the phenomenon of travelling whispers with a series of specularly reflected sound rays making up chords of the circular gallery. Clinging to the walls the sound should decay in intensity only as the inverse of the distance — rather than the inverse square as in the case of a point source of sound radiating in all directions. This accounts for the whispers being audible all round the gallery. Rayleigh developed wave theories for St Paul’s in 1910〔(Rayleigh, Philos. Mag. 20, 1001,1910. )〕 and 1914.〔(Rayleigh, Philos. Mag. 27, 100, 1914. )〕 Fitting sound waves inside a cavity involves the physics of resonance based on wave interference; the sound can exist only at certain pitches as in the case of organ pipes. The sound forms patterns called modes, as shown in the diagram.〔 Many other monuments have been shown〔(V. Raman, Proc. Indian Ass. Cult. Sci. 7, 159, 1921-1922 )〕 to exhibit whispering-gallery waves, such as the Gol Gumbaz in Bijapur and the Temple of Heaven in Beijing. In the strict definition of whispering-gallery waves, they cannot exist when the guiding surface becomes straight.〔(M. Brekhovskikh, Sov. Phys. Acoust. 13, 462, 1968 )〕 Mathematically this corresponds to the limit of an infinite radius of curvature. Whispering-gallery waves are guided by the effect of the wall curvature. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Whispering-gallery wave」の詳細全文を読む スポンサード リンク
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