Mercury-free metal-halide lamp

摘要

A pair of electrodes (3) are provided in an arc tube (1) I/S is 20 (A/mm<2>) or less on a condition that an area of a cross section at a tip of the electrodes (3) is S (mm<2>) and an operating current between the electrodes (3) is I (A). According to this constitution, a long lamp life can be obtained without causing a rise in the lamp voltage and the blackening of the arc tube (1) by the evaporation of the electrodes while operation time becomes longer.