*Question E6F02:
What happens to photoconductive material when light shines on it?*  

*Correct Answer is  A: Resistance decreases*  

### AI Response: (may contain errors)  

When light shines on photoconductive material, the correct answer is:

**A: Resistance decreases**

### Explanation:

1. **Why the correct answer is correct:**
   - Photoconductive materials, such as cadmium sulfide (CdS) or lead sulfide (PbS), have a property where their electrical resistance decreases when exposed to light. This occurs because the energy from the light photons excites electrons, allowing them to move more freely within the material. As a result, the number of charge carriers increases, leading to a decrease in resistance.

2. **Why the other choices are incorrect:**
   - **B: Resistance increases**: This is incorrect because the introduction of light increases the number of free charge carriers, which lowers resistance, not increases it.
   - **C: Reflectivity increases**: This is not necessarily true. While some materials may reflect more light when they are illuminated, photoconductive materials primarily change their conductivity rather than their reflectivity in a significant way.
   - **D: Reflectivity decreases**: Similar to choice C, this is not a general characteristic of photoconductive materials. The change in reflectivity is not the primary effect of light exposure; the main effect is the change in resistance.

### Useful Concepts:
- **Photoconductivity**: The phenomenon where the electrical conductivity of a material increases when it is exposed to light.
- **Charge carriers**: Electrons and holes that contribute to electrical conduction. In photoconductive materials, light generates additional charge carriers, enhancing conductivity.

Understanding these principles will help you grasp the behavior of photoconductive materials in various applications, such as light sensors and photodetectors.