Which of the following best describes the sensors designed to project and detect a light...

Photoelectric sensors are specifically designed to project and detect a light beam across an area. They are commonly used in applications such as perimeter protection, object detection, and safety systems. These sensors work by emitting a light beam (infrared or visible) and detecting any interruption of this beam. Options like smoke, thermal, and air-aspirating sensors pertain to fire detection and temperature monitoring, which are unrelated to light-based detection systems.