The invention proposes an arrangement of luminescent materials for excitation by means of a radiation source and involving the use of a luminescent material having a Ce-activated garnet structure A.sub.3B.sub.5O.sub.12, in which the first component A contains at least one element from the group consisting of Y, Lu, Se, La, Gd, Sm and Tb and the second component B represents at least one of the elements Al, Ga and In, and a plurality of the luminescent materials are mixed together. An associated wavelength-converting casting compound and an associated light-source arrangement are further proposed.