a light radiator includes a semitransparent tubular container , a large number of transparent plates arranged in series inside of said tubular container in such a way as to be inclined in the same direction as the axis of said container , a light - guiding , cable - connecting portion provided at one end of the container to connect thereto the output end of a light - guiding cable , a lens inserted between the light - guiding , cable - connecting portion and the transparent plate and a motor for rotating the tubular container . the transparent plates each have at least a partial reflecting surface and their reflecting surfaces are made larger in size because of being farther from the lens in order to reflect a substantial , even amount of light rays . a light radiator capable of radiating solar rays which are focused by lenses introduced into a light - guiding cable and of being transmitted therethrough to the light radiator for radiating them to such objects as plants etc .