envelope 20 from the foil strips 41 42 can each be essentially any material which electrically and mechanically connects well to molybdenum since molybdenum connects well to molybdenum either or both of the electrodes 53 54 and the pins 41 42 may be of this material alternatively tungsten connects well such as by welding to molybdenum so that the electrodes 53 54 may be beneficially formed of this material also the improved gas discharge lamp 10 in accordance with the present invention contains a selected gas and mercury vapor in the sealed cavity defined by envelope 20 disk 30 and base region 40 when the gas discharge lamp 10 is electrically connected normally by plugging to a source of electrical potential between electrical pins 51 and 52 then this potential appearing across electrodes 53 and 54 causes ionization of the gas within the gas discharge lamp 10 and causes an electrical arc to be developed and sustained for so long as this voltage is maintained this electrical arc is concentrated in density at the orifice 57 of tube 55 and at the orifice 58 of the tubular member 56 these two locations appear as two bright spots in the light emission from the lamp 10 in operation of gas discharge lamp 10 an electrical discharge path through ionized gas within the region of the lamp 10 proximate to disk 30 causes emission of light radiation at a single frequency if this light radiation is of a short wavelength as is the case when the ionized gas is mercury vapor then the light will not substantially pass through any portions of envelope.