What are the three types of Photocell configurations?

• A. Reflected, refracted, and diffracted
• B. Direct, indirect, and mixed
• C. Transmitted beam, retro-reflective, and diffuse sensing
• D. Smoked, clear, and tinted

Answer: (C)

Photocell configurations in photoelectric sensing come in three common arrangements: through-beam (transmitted beam), retro-reflective, and diffuse sensing. In through-beam, the light emitter and receiver are separate; the beam travels to a distant receiver and is interrupted by the target, giving long-range sensing and high reliability. In retro-reflective, the emitter and receiver are together in one unit and a reflector is placed opposite; the beam reflects back to the receiver and the target interrupts the return path. In diffuse sensing, the target itself reflects light back to the receiver, so there’s no separate reflector needed; this is simple and inexpensive but typically shorter in range and sensitive to surface characteristics. The other options describe optical phenomena or material properties rather than how a photocell is configured for sensing.