Final answer:
The red sector in the characteristic of the light on a lighthouse indicates a danger area.
Step-by-step explanation:
The red sector in the characteristic of the light on a lighthouse indicates a danger area. It is used to warn ships of potential hazards, such as rocks or shoals, and to guide them away from these areas. The flashing white light serves as a general navigational aid, while the red sector provides specific information about a hazardous area.