Final answer:
The period of a lighted aid to navigation refers to the length of time between flashes of the light, much like measuring time intervals in physics to observe light behavior over distance. Option b is the correct answer.
Step-by-step explanation:
The period of a lighted aid to navigation refers to the length of time between flashes of the light. This is fundamentally a physics concept that deals with measuring time intervals, particularly the periodic events characteristic of lighthouses and beacons, which are critical for maritime navigation.
The given illustrations in FIGURE 28.5 and FIGURE 28.6 can be analogously related to the understanding of how light behaves over distance and time, similar to how navigation aids use light to convey signals over time.
In the context of the question, and making an analogy to the movement of light as described in the figures provided, the period would be the time taken for the cycle of light (flash-on to flash-on) to complete. Thus, it does not refer to the construction date, the duration of the longest single flash, or the time taken by the light to travel a specific distance, but rather the entire cycle duration, including the dark intervals between flashes.
Therefore, the correct option that defines the period of a lighted aid to navigation is B. the length of time between flashes of the light.