Three fluorescent lamps: a circular tube lamp with magnifier, 1967; a battery operated hand lamp, 1966; and a bench lamp, 1957. Fluorescent lighting came into widespread use during World War II because of its high efficiency. An electrical discharge in mercury vapour and argon (or other rarified gas) produces the ultra violet light. Fluorescent materials on the inner wall of the glas tube convert the ultra violet into visible light. The powerful hand-lamp shown in the middle, operates from a twelve volt dry battery.
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