of the outer wall 24 of the outer tube 18 around the light discharging portion 25 to constitute a reflecting mirror 26 in the form of an internal mirror meanwhile an inner wall 27 of the outer tube 18 is formed as a flat transparent glass plate the convex lens 14 is disposed such that the optical axis thereof may coincide with the major axis of the spheroidal mirror of the reflecting plate 11 and a focus thereof may coincide with the light emitting portion 20 of the discharge tube 13 the reflecting plate 11 and the discharge tube 13 are assembled to each other such that the outer tube 18 of the discharge tube 13 is inserted in position into the forward opening 15 of the reflecting plate 11 with the inner wall 27 thereof directed inwardly that is leftwardly in fig1 next coupling portions of the inner wall 27 and reflecting plate 1 are coupled to each other at outer peripheries thereof by means of a jig or the like in the light apparatus described above the light discharging portion 25 of the outer tube 18 of the discharge tube 13 is formed from a cold filter this.