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opeidoscope

noun opei·do·scope \ ōˈpīdəˌskōp \
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Definition of opeidoscope

: an instrument consisting essentially of a tube across one end of which is stretched a thin flexible membrane bearing a small mirror and used for exhibiting upon a screen by rays reflected from the mirror vibratory motions caused by sounds

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Origin and Etymology of opeidoscope

Greek opa (accusative) voice + eidos form + English -scope

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