If one side of the slot is boxed in, there is radiation in the plane of the sheet as suggested by the pattern in Fig. 13-9b. with a finite sheet the pattern usually exhibits a scalloped or undulating characteristic, as suggested in Fig. 13-9. As the length L of the sheet is increased, the pattern undulations become more numerous but the magnitude of the undulations decreases, so that for a very large sheet the pattern conforms closely to a circular shape