Answer: Frequency exactly equal to the threshold frequency.
- A Frequency much greater than the threshold frequency
- B Maximum possible intensity
- C Wavelength shorter than the threshold wavelength
- D Frequency exactly equal to the threshold frequency
Correct answer: D. Frequency exactly equal to the threshold frequency
Explanation: At threshold frequency, the maximum kinetic energy of the emitted electrons is zero. Hence the stopping potential is also zero.
In the photoelectric setup, light striking the metal plate ejects electrons that cross the evacuated tube to the collector, producing a measurable current on the ammeter.
Concept context
Photoelectric effect, de Broglie waves, Bohr's model, atomic spectra.