Answer: 0.16 nm.
- A 0.20 nm
- B 0.16 nm
- C 0.25 nm
- D 0.40 nm
Correct answer: B. 0.16 nm
Explanation: Since λ = h/p, the new wavelength is 0.20/1.25 nm = 0.16 nm.
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.