What type of light is the flame sensor sensitive to?

The flame sensor is designed to detect different types of light emissions associated with flames, which include infrared, visible, and ultraviolet light. Flames emit radiation across a range of wavelengths, and the sensors are calibrated to react to these specific emissions.

Infrared light is produced by the heat of the flame, while visible light represents the color of the flame itself. Ultraviolet light is emitted in smaller quantities but is significant, especially in certain types of combustion. By being sensitive to all three types of light, a flame sensor can effectively monitor for the presence or absence of a flame in various conditions and types of fuel. This capability ensures reliable operation, contributing to safety systems in boilers, furnaces, and other combustion applications.

In contrast, the other choices limit the sensitivity of the flame sensor to only one specific type of light, which would reduce its effectiveness and reliability in flame detection.