A light bulb has a light guide configured as a hollow body surrounding an internal volume. The light guide is open at its proximal and distal ends, and has inner and outer surfaces and an end surface at the proximal end that provides a light input edge. A solid-state light source is optically coupled to the light input edge of the light guide such that light from the solid-state light source travels in the light guide by total internal reflection. The solid-state light source is thermally coupled to a housing at the proximal end of the light guide. The housing contains vents for air flow and convection cooling through the internal volume. Light-extracting optical elements at least one of the inner surface and the outer surface of the light guide are for extracting light from the light guide.