Abstract: There is provided illuminating apparatus including an illuminating channel 10 defined between an incident surface 11, an emergent surface 12, an upper surface 13 and a lower surface 14. The upper surface 13 includes end portions 15 which may be adhered to the lower end portions 16 of an adjacent illuminating channel. The portion of the upper surface 13 between the end portions 15 comprises a steeply inclined outer portion 17, a horizontal central portion 20 and a shallow inner inclined portion 21. Light entering the incident face 31 at a low angle of incidence is reflected by total internal reflection in turn from the lower outer surface 32 of a first cavity 33, the central portion of the upper surface 34 of a second cavity 35, and then the inner lower surface 36 of the first cavity 33 before emerging from the emergent face 37.