What happens to the aneroid wafers in the altimeter during a decrease in static pressure?

When there is a decrease in static pressure, the aneroid wafers in the altimeter respond by collapsing. This occurs because the aneroid wafers are designed to react to changes in atmospheric pressure. As the external air pressure decreases, there is less pressure exerted on the outside of the wafers, causing them to collapse inward. This movement is translated into altitude readings on the altimeter, indicating that the aircraft is ascending or that the altitude relative to a certain pressure level is increasing.

In contrast, if the pressure were to increase, the wafers would expand as they are pressed outward by the rising ambient pressure. Understanding this mechanism is crucial for pilots, as it directly affects altitude readings and navigation. The other options do not accurately describe the behavior of the aneroid wafers in response to changes in static pressure.