What Is -1 Expressed as a Phase Factor?
A) $e^{i \pi / 2}$

Multiple Choice

What is -1 expressed as a phase factor?

A) $e^{i \pi / 2}$
B) $e^{-i \pi / 2}$
C) $e^{i \pi}$
D) $e^{i 2 \pi}$
E) Something else (specify)