Photoconductivity
Photoconductive materials become more conductive, (have less resistance), when exposed to light. Photoconductivity affects are seen most prominently in crystaline semiconductors. The amount of increased conductivity depends on the material and on the wavelength of light illuminating it. For example, cadmium sulfide is most sensitive to visible light, while lead sulfide is most sensitive to infrared light.
Exam Questions:
What is photoconductivity?
A. The conversion of photon energy to electromotive energy
B. The increased conductivity of an illuminated semiconductor
C. The conversion of electromotive energy to photon energy
D. The decreased conductivity of an illuminated semiconductor
What happens to the conductivity of a photoconductive material when light shines on it?
A. It increases
B. It decreases
C. It stays the same
D. It becomes unstable
What characteristic of a crystalline solid will photoconductivity change?
A. The capacitance
B. The inductance
C. The specific gravity
D. The resistance
Which material will exhibit the greatest photoconductive effect when illuminated by visible light?
A. Potassium nitrate
B. Lead sulfide
C. Cadmium sulfide
D. Sodium chloride
Which material will exhibit the greatest photoconductive effect when illuminated by infrared light?
A. Potassium nitrate
B. Lead sulfide
C. Cadmium sulfide
D. Sodium chloride
Which of the following materials is affected the most by photoconductivity?
A. A crystalline semiconductor
B. An ordinary metal
C. A heavy metal
D. A liquid semiconductor