Answer:
D Photoelectric effect
Explanation:
When light of a certain frequency which is above the cut off frequency is incident on a metal, electrons are emitted from its surface. These electrons are called photo electrons. The number of photo electrons released will depend on the intensity of the incident light. This flow or release of electrons develops an emf and is called as the photoelectric current.
Applications of photoelectric current include photo conductive cells, photoemissive cells, solar cells etc.
