  Although the photoacoustic effect is most commonly generated by pulsed or
amplitude modulated continuous optical sources, it is possible to generate
acoustic waves by moving a constant amplitude, continuous light beam. If the
light beam moves at the speed of sound, an amplification effect takes place
which can be used in trace gas detection. Here, the properties of the
photoacoustic effect are investigated for a continuous optical beam moving in a
one-dimensional resonator. The solution shows the additive effects of sweeping
the optical beam the length of the cell and back.
