Gage, Alfred P. (Alfred Payson), 1836-1903 · Boston, London, Ginn · leaf 627
d-waves may hegenerated by rays of light, and speech be transmitted through theinstrumentality of ether-vibrations. Kays of light of the sun, anelectric lamp, etc. fall upon a mirror M (Fig. 492) and are reflectedto a disk D of silvered mica. A person speaking into 0 causes the disk to vibrate,… … FlO. 492. and are reflected thence upon a selenium cell P. THE ELECTRIC FIRE-ALARM. 605 fore exposed to an undulatory radiation corresponding to thesound-vibrations. The conductivity of selenium is susceptible torapid changes caused by slight changes of radiant energy fallingupon it. Hence a…
Physics
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