The blue-green Balmer line of hydrogen with is selected with a filter and shone on…
PHYSICS · Multi-part · Fermi University Physics · Quantum Mechanics · Origins of quantum theory · Origins of quantum theory
Quantum Mechanics: From the Photon to the Hydrogen Atom, Ch Line spectra, the Bohr atom and the old quantum theory
Problem
The blue-green Balmer line of hydrogen with n2=4→n1=2 is selected with a filter and shone on the caesium cathode of an evacuated photoelectric cell. The work function of caesium is W=2.14 eV. One photon ejects one electron, and Kmax refers to the electrons that leave the metal without losing energy inside it. Take RH=1.097×107m−1, hc=1240 eV nm, me=9.109×10−31 kg and 1eV=1.602×10−19 J.
((a)) Find the wavelength of the line, in nm.
((b)) Find the maximum kinetic energy of the photoelectrons, in eV.
((c)) Find the greatest speed with which an electron leaves the cathode, in ms−1.