What event will cause the Emergency Exit Lights to become illuminated?

The Emergency Exit Lights are designed to provide illumination during an emergency situation to guide passengers and crew to the exits when the normal lighting might be unavailable. The correct event that causes these lights to become illuminated is the interruption of aircraft normal electrical power.

In the event of a power failure, the emergency lighting system automatically activates to ensure visibility in critical situations. This system operates independently of the main power supply, using its own backup power source, typically rechargeable batteries, to function. This redundancy is crucial for safety, as it ensures that emergency exit routes remain visible even if all other lights in the cabin go out.

While other circumstances such as a loss of cabin pressure or activation of the fire suppression system may indicate an emergency, they do not directly trigger the emergency exit lights. The manual activation by cabin crew is a possibility, but it is typically intended for situations where the crew anticipates a need for emergency exit lighting due to specific circumstances, such as an imminent evacuation or fire. However, the primary automatic activation is triggered by a loss of normal electrical power, which highlights the system's design focus on ensuring safety without reliance on crew intervention.