WHY SOUND MAKE A LIGHT SPOT DANCE?

When sound waves hit a thin surface, they can create vibrations that cause the surface to move slightly. This movement can be enough to make a light spot appear to dance or move around due to the vibrations induced by the sound waves. The phenomenon is known as a "Chladni figure" or "singing sand" effect, where different frequencies of sound can create different patterns of movement in the light spot.