Answer: ±1/2.
- A 0, ±1
- B ±1/2
- C 0, 1, 2
- D Any integer
Correct answer: B. ±1/2
Explanation: Spin quantum number ms = ±1/2 (spin-up or spin-down). This is a fundamental quantum property with no classical analogue.
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.