Dark adaptation requires ___________________ or more, but may be destroyed in less than ___________________.

Dark adaptation refers to the process through which the eyes adjust to low-light conditions, allowing for improved vision in darkness. This process typically requires about 30 minutes for the human eye to fully adapt to low-light situations, as photoreceptor cells in the retina, particularly rods, become increasingly sensitive in the absence of bright light.

During this adaptation phase, the photopigment rhodopsin in the rods regenerates, enhancing visual sensitivity. However, this adaptation can be temporarily disrupted by exposure to bright light for just a brief moment, often for less than 30 seconds. The highlighted timeframe emphasizes the fragility of dark adaptation, demonstrating how quickly it can be compromised.

Understanding the specifics of these timeframes is crucial for boat crew members, especially in situations where visibility decreases and the ability to see clearly in the dark is vital for safety and navigation.