Directing electromagnetic radiation

A method for regulating flow of electromagnetic radiation comprising

• providing a source of electromagnetic radiation;
• arranging the source to emit electromagnetic radiation in a direction into a volume,
• placing a reflective surface in the volume to receive the radiation thereon;
• defining on the reflective surface an array of two or more ridges which are arranged side by side in a first direction across the reflective surface;
• wherein each ridge projects forwardly from a base toward the source;
• wherein each ridge has a first reflective ridge surface and a second reflective ridge surface where the first and second surfaces extend longitudinally in a second direction transverse to the first direction;
• wherein the first reflective ridge surface and the second reflective ridge surface converge toward an apex extending longitudinally along the second direction;
• wherein the first reflective ridge surface and the second reflective ridge surface are arranged so that at least some of the radiation impinges on at least one of the first reflective ridge surface and the second reflective ridge surface;
• wherein the first reflective ridge surface and the second reflective ridge surface are arranged such that the radiation incident on the first reflective ridge surface is primarily reflected in a first reflection direction and such that the radiation incident on the second reflective ridge surface is primarily reflected in a second reflection direction different from that of the first reflection direction.