A type of curve used in interpreting pulse IP data, also called a pulse curve. Beta, the ratio of observed apparent chargeability to the true chargeability of the lower medium (a bilogarithmic weighting function developed from IP theory), is proportional to IP phase angle. A beta curve for a simple single horizontal layer where only the lower material is polarizable shows the resistivity contrast factor as a function of the ratio of array interval to depth (alpha) and beta. See Seigel (1959, Chap. 2).