What is (a) Something having a polished surface for reflecting light or heat, as a mirror, a speculum, etc. (b) A reflecting telescope. (c) A device for reflecting sound called?

reflector — (Physics) (a) Something having a polished surface for reflecting light or heat, as a mirror, a speculum, etc. (b) A reflecting telescope. (c) A device for reflecting sound. (Webster's 1913.)

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