Quantum physics: Practice Questions

What is a quantum of electromagnetic energy called?

An electron in an isolated atom undergoes a transition between two energy levels. The energy of the initial level is \(-1.51\text{ eV}\) and the energy of the final level is \(-3.40\text{ eV}\).

What is the wavelength of the photon emitted during this transition?

Monochromatic light of wavelength \(300\text{ nm}\) is incident on a metal surface. The work function of the metal is \(2.4\text{ eV}\). Photoelectrons are emitted from the surface. What is the minimum de Broglie wavelength of these emitted photoelectrons?

Which equation correctly represents the de Broglie wavelength \(\lambda\) of a moving particle with momentum \(p\)?

Light of frequency \(1.2 \times 10^{15}\text{ Hz}\) is incident on a metal surface, causing photoelectrons to be emitted. The work function of the metal is \(3.3 \times 10^{-19}\text{ J}\). Given that the Planck constant \(h = 6.63 \times 10^{-34}\text{ J s}\), what is the maximum kinetic energy of the emitted photoelectrons?

Calculate the de Broglie wavelength, in nanometres (nm), of an electron that has been accelerated from rest through a potential difference of \(4.5 \, \text{kV}\).

(a) Describe the evidence provided by the photoelectric effect for the particulate nature of electromagnetic radiation.
(b) The work function energy of a certain metal is \(2.26 \text{ eV}\).
(i) Calculate the threshold frequency for this metal.
(ii) Electromagnetic radiation of wavelength \(380 \text{ nm}\) is incident on the metal surface. Calculate the maximum speed of the emitted photoelectrons.
(c) Calculate the de Broglie wavelength of a photoelectron moving with the maximum speed calculated in (b)(ii).