partition fins 1210 extend along a direction from top to bottom two neighboring fins 1210 are spaced apart from one another with a channel therebetween the led module 120 comprises a plurality of leds not labeled installed at the bottom of the heat conducting body a hemispherical transparent cover 125 is engaged with the bottom of the heat sink 121 and covers the led module 120 the transparent cover 125 is so dimensioned and positioned that bottom intakes of the channels between the fins 1210 are exposed downward to the surrounding air without being blocked by the cover 125 thus air can easily flow upwardly along the cover 125 into the channels between the fins via the bottom intakes thereof the shell 16 is inverted frustum shaped and comprises a top plate 161 a bottom plate 163 and a lateral wall 162 interconnecting with the top plate 161 and the bottom plate 163 the lamp holder 14 is mounted at the top plate 161 for connecting the connector 124 of the led bulb 12 the lateral wall 162 is around the led bulb 12 and has an angled inner surface 164 defined at an acute angle with respect to the bottom plate 163 the lateral wall 162 can be made of metal material which can reflect light the bottom plate 163 is transparent a part of light generated by the led module 120 radiates downwardly directly through the transparent bottom plate 163 another part of the light generated by the led module 120 is reflected by the inner surface 164.