Experimental science. Elementary, practical and experimental physics (1890)
Hopkins, George M. (George Milton), 1842-1902 · New York, Munn & co. · leaf 184
e focus of the reflectormay be projected in parallel lines over long distances, butin practice a speaking trumpet is found to be better for thispurpose. The engraving shows but one of the applicationsof the reflector. It would be a simple matter to providefor a deaf person an instrument on this… … SClJVv. Reflection of Light and Sound. may also be appUed to an auditorium to project the voice ofthe speaker in any required direction. To concentrate and project light, heat, and sound bymeans of concave mirrors is generally supposed to necessi-tate the use of expensive parabolic mirrors,…
Physics · Lantern projection · Electric apparatus and appliances
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