An electrodeless microwave discharge lamp includes a substantially sealed microwave cavity, an envelope disposed within the sealed cavity, the envelope containing a fill which emits light when excited by microwave energy, and means for circulating air inside the sealed microwave cavity. For example, the means for circulating air includes a ceramic reflector inside the cavity with defined air flow channels. The lamp may further include a fan for moving air through the defined air flow channels. For example, the envelope is adapted to rotate during operation and blades are mounted on the stem of the bulb inside the sealed cavity. A sealed light distribution system includes a hollow light pipe having an opening at one end and an annular ring of elastomeric material secured to the open end of the light pipe. When used with a lamp with a reflector, the reflector is received in the opening of the ring and the ring forms a seal around the outside of the reflector. Another light distribution system includes a multi layer light conduit having at least two full layers formed by a single spiral wound plastic sheet. Another light distribution system includes a reflector positioned to receive light from a light source to transform at least some of the light into shallow angle light relative to a light emitting wall of an enclosure. The light is distributed through the enclosure by specular reflection of the shallow angle light.
 Certain inventions described herein were made with Government support under Contract Nos. DE-FC26-00NT40988 or DE-FC-99FT40635 awarded by the Department of Energy. The Government has certain rights in those inventions.