Question
What happens to photoconductive material when light shines on it?
Answer Options
- A) Resistance decreases
- B) Resistance increases
- C) Reflectivity increases
- D) Reflectivity decreases
Correct Answer: A
Explanation
Photoconductivity is the phenomenon where a material’s ability to conduct electricity increases when it absorbs electromagnetic radiation (light). Materials that exhibit this property, such as cadmium sulfide (CdS) or crystalline semiconductor layers, are used in light detectors and sensors.
When light shines on a photoconductive material, the photons transfer energy to the bound electrons, creating mobile charge carriers (electrons and holes). The presence of these additional free carriers increases the material’s conductivity. Therefore, what happens to photoconductive material is that its Resistance decreases (and conductance increases), making it an electronically controlled variable resistor activated by light.
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