What noticeable change does the photoconductive effect in crystalline solids produce?

The photoconductive effect in crystalline solids refers to the change in electrical conductivity when the material is exposed to light. When photons are absorbed by the crystalline solid, they provide enough energy to excite electrons from the valence band to the conduction band, effectively creating free charge carriers. This increase in free electrons results in a noticeable drop in the resistance of the solid.

As the resistance decreases, the material becomes more conductive; this is the fundamental principle behind photoconductivity. The greater the intensity of the light, the more electrons can be excited, leading to further reductions in resistance. Therefore, the correct answer highlights how the photoconductive effect primarily influences the resistance of the solid, allowing it to conduct electricity more easily when exposed to light.

In contrast, changes in capacitance, inductance, or temperature may occur in some contexts but are not the direct effects associated with the photoconductive phenomenon. Capacitance and inductance pertain to a material's ability to store and manage electric charge and magnetic fields, respectively, while temperature changes involve thermal properties unrelated to the photoconductive effect itself. Thus, the focus on resistance is central to understanding the implications of photoconductivity in crystalline solids.