Metal halide lamp that has desired color characteristic and is prevented from non-lighting due to leakage of arc tube attributable to crack occurring at thin tube, and lighting apparatus adopting the metal halide lamp

摘要

Provided is a metal halide lamp capable of being dimmed, which is prevented from non-lighting due to leakage of an arc tube attributable to a crack occurring at thin tubes, as well as realizing a desired color characteristic. The metal halide lamp has an arc tube that includes an envelope made of translucent ceramic, a pair of electrodes, and metal halides, the metal halides including rare earth metal halide, sodium halide, and magnesium halide, the rare earth metal halide being at least one of dysprosium halide, thulium halide, holmium halide, cerium halide, and praseodymium halide, and the magnesium halide being at least one of magnesium iodide and magnesium bromide, where when a maximum lamp power P (W) is in a range of 70 W to 250 W, the following relations are satisfied: 0.0345A+0.0028B0.0015P+0.0475; A≧0.021P+0.313; and B≧10.0, where A (mg) represents a total content of the metal halides, and B (mol %) represents a content ratio of the magnesium halide to the metal halides.