What is the purpose of a light gun signal?

The purpose of a light gun signal is fundamentally about providing visual communication, especially when other means of communication, like radio, are unavailable. When an aircraft loses radio communication, ground personnel can use a light gun to visually convey instructions to pilots. This method is especially crucial during situations where clear communication is necessary for safety and operational efficiency, such as in airports with significant traffic. The signals can indicate various commands, including takeoff, land, taxi, and stop, allowing pilots to safely navigate the airspace and ground.

The other options revolve around different aspects of communication or guidance but do not accurately capture the primary purpose of light gun signals in emergencies where radio communication failure occurs.