
INTRODUCTION 21
Had we chosen to replace E by E
∗
and vice versa, we would have obtained the same result
with
E
r
= Ee
−
√
−1ωt
+E
∗
e
√
−1ωt
(Alternative form not used). (1.53)
Thus the choice of what we call “positive” frequency is arbitrary. Furthermore, the expression
√
−1 is represented in various disciplines as either i or j. Therefore, there are four choices for
the exponential notation. Two of these are in common use. Physicists generally prefer to dene
the positive frequency term as
Ee
−iωt
(1.54)
and engineers prefer
Ee
+jωt
. (1.55)
The letter j is chosen to prevent confusion because of electrical engineers’ frequent use of
i to denote currents in electric