Wine glasses exhibit four nodes due to their fundamental frequency oscillation, which is a characteristic of circular objects. This oscillation involves a compression in one direction and an expansion in another, resulting in four nodes and four anti-nodes. The fundamental frequency of the glass itself remains constant, but the frequency can change when the water level varies, as the glass must move more water during oscillation. Increased water level requires more time for the same displacement, affecting the overall frequency. Understanding these principles clarifies the acoustic properties of wine glasses.
