When irreducible representations are given in diagrammatic form, it is possible to show direct products pictorially. By giving a similar description of the electric vector associated with a light wave, group-theoretical selection rules (the requirement of a totally symmetric direct product) can also be shown in pictorial form. The [upsilon](CO) vibrations of Mn(CO)[subscript 5]Br are considered as an example; some relative band intensity conclusions arise naturally from the pictorial description. (Contains 16 figures, 3 tables and 2 notes.)