A light includes a light-producing inner tube, and an outer tube positioned around the light-producing inner tube; the light-producing inner tube has electrical terminals at two ends thereof, which sticks out of the outer tube; the outer tube has a light reflecting film on an outer side of a first portion thereof; an inner side of the first portion of the outer tube is processed so as to have a rough and lumpy surface, which can cause light produce by the light-producing inner tube to travel in all directions; the outer tube has a fluorescent layer on each of inner and outer sides of a second portion thereof, which make the second portion of the outer tube more pervious to light.