Abstract: In an electrodeless fluorescent lamp of the type including a sealed, light transmissive, envelope including an elongate inner wall defining an open-ended cavity and an outer wall surrounding the inner wall to form a generally annular, hollow cavity therebetween, the annular cavity being charged with an ionizable gaseous medium, an induction coil positioned within the open-ended cavity, and a radio frequency oscillator connected to the coil, the coil and the oscillator initiating and maintaining ionization of the medium to form an ultraviolet light emitting discharge, the inner surface of the outer wall of the envelope being coated with a phosphor which emits visible light when excited by ultraviolet light, the improvement wherein the outer surface of the inner wall is coated with a layer of an electrically insulative ultraviolet light reflective material which is overcoated with a phosphor layer. Such improvement yields an increase in visible light production of the order of 50% to 100%.

Abstract: An electrodeless discharge lamp has an ionizable medium comprising a particular gas composition at a particular pressure within a sealed envelope. Radio frequency electrical power is applied to an induction coil, the magnetic induction field of which is coupled to the medium. For a particular radio frequency, the magnitude of the induction field is selected to maximize the light emitted by the discharge per watt of radio frequency power coupled thereto. The radio frequency is preferably between 3 megahertz and 300 megahertz.