Physics
Physics
Problem
A beam of monochromatic light of frequency falls on a clean metallic surface and causes photo-emission. (i) Define a photon and state how the energy of a photon depends on the frequency of light. (ii) Explain why, for a fixed frequency greater than the threshold frequency of the metal, increasing the intensity of incident light increases the photoelectric current but does not alter the stopping potential. (iii) If the intensity of the incident beam is doubled while the frequency is kept the same, what happens to the number of photons striking the surface per unit time? Give a reason for your answer.Intuitive explanation
The photoelectric effect reveals how light behaves as discrete energy packets called photons, each carrying energy proportional to frequency. Understanding this requires distinguishing between the number of photons (which depends on intensity) and the energy per photon (which depends only on frequency)—intensity controls how many electrons are ejected, but frequency controls how energetic each electron becomes. This separation is key to explaining why stopping potential stays constant while current increases with brighter light.
Intuitive explanation
The photoelectric effect reveals how light behaves as discrete energy packets called photons, each carrying energy proportional to frequency. Understanding this requires distinguishing between the number of photons (which depends on intensity) and the energy per photon (which depends only on frequency)—intensity controls how many electrons are ejected, but frequency controls how energetic each electron becomes. This separation is key to explaining why stopping potential stays constant while current increases with brighter light.