noun
photoelectric tube
Technical term for a vacuum tube that converts light into electrical current, used in early light sensors and scientific instruments.
光電管は光の強さを測るのに使われる。
A photoelectric tube is used to measure light intensity.
A photodiode is a modern semiconductor light sensor, whereas 光電管 is an older vacuum-tube technology.
Compound of 光電 (photoelectric) and 管 (tube). The exact historical derivation is uncertain; the spelling is conventionally associated with the meaning.