Answer to Question #141989 in Quantum Mechanics for Jackson

Question

An electron is accelerated through a potential difference of 12.1 V.
n=5 -0.54eV
n=4 -0.8 eV
n=3 -1.5 eV
n=2 -3.4 eV
n=1 -13.6 eV
(a) How much kinetic energy has it gained in (i) electronvolts (ii) joules? (b) This electron hits a hydrogen atom and excites it. (i) Explain what is meant by excitation

Answer 1

(a)

$E=e\Delta\varphi=1.6\cdot10^{-19}\cdot12.1=1.9\cdot10^{-18}$ J (ii)

$E=12.1$ eV (i)

(b)

 Excited state is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum).