  In this paper we present the method and experimental results of the
investigation of a longitudinal component of relativistic electron
electromagnetic field in the shadow area of a transversal component. We show
experimentally, that in a region, comparable with the formation length area no
shadowing effect of the longitudinal component of relativistic electron
electromagnetic field appears. This is important for understanding of
possibility of the shadowing effect in Smith-Purcell radiation and some other
radiation types.
