# Wave propagation, +z or -z

1. Apr 16, 2009

### sokrates

This is probably a silly question -- but I have been thinking about it, and I can't convince myself. So, I'd be greatly happy if you could solve my apparent "dilemma".

In electromagnetics, for sinusoidal voltages, we use the phasor notation and express a
positive travelling wave ( +Z direction)
as follows:

$$E_+ = A_0 e^{-i \beta z }$$

where as in quantum mechanics a positive travelling wave (+Z direction) is written as follows (correct me if I am wrong)

$$\Psi_+ = A_0 e^{+i \beta z}$$

where beta's are wavenumbers.

Where am I messing this up?