Final answer:
The pulsation in the luminosity of variable stars is caused by the expansion and contraction of the star itself, not the changing opacity of their atmosphere.
Step-by-step explanation:
False. The pulsation in the luminosity of variable stars is not driven by the changing opacity of their atmosphere. It is actually caused by the expansion and contraction of the star itself. This can be measured using the Doppler effect, where the lines in the star's spectrum shift towards the blue as the surface moves towards us and then shift towards the red as the surface shrinks back. As the star pulsates, its overall color and temperature also varies, resulting in changes in its luminosity.