The photoelectric sensor operates on the principle of which of the following?

• A. Photoconduction
• B. Photoconductivity
• C. Photoelectric effect
• D. Photoluminescence

Answer: (A)

Light hitting the photosensitive element changes how easily electricity can flow through it. In many photoelectric sensors this element is a light-sensitive resistor, which becomes more conductive when illuminated because photons generate charge carriers. That light-induced increase in conductance is the essence of how the sensor detects light or a beam being interrupted. This process is photoconduction. It’s the best fit because it directly describes the device’s operating change—conductivity rising with light. The other terms describe different phenomena: the photoelectric effect involves emission of electrons, which isn’t what these sensors rely on; photoluminescence is about a material emitting light after excitation, not detecting light; photoconductivity is the general property of becoming more conductive under light, which is closely related but less specific to the actual sensing action compared to photoconduction.