Which sensor type uses emission and detection of light to sense presence?

• A. Inductive
• B. Capacitive
• C. Photoelectric
• D. Hall effect

Answer: (C)

Optical sensing relies on emitting light and detecting how that light changes to determine if something is present. A photoelectric sensor does this by sending out a light beam and watching what the receiver detects. If the beam is interrupted or its reflection changes due to an object in the path, the receiver responds, signaling presence. This non-contact method works with many materials and can be configured as through-beam, retroreflective, or diffuse-rattered types, depending on the setup.

Inductive sensors, by contrast, detect metal objects through changes in an electromagnetic field, not light. Capacitive sensors sense presence by changes in capacitance caused by nearby objects, regardless of metal or dielectric, and Hall effect sensors detect magnetic field changes, typically from magnets. So the use of emitted light and detection of that light points to the photoelectric option.