Abstract: The origin for ＂the tight vector can be expressed by electricity vector under the normal case＂ in op- tical textbooks is discussed. The analysis shows that the optical rotation phenomena and the light vector of negative refractive index media can not be expressed fully by the electricity vector. We still point out that the basic connotation of the concept shauld be developed with the development of the discipline.

Key words: light vector, optical rotation, negative refractive index media