Physics
Physics
Problem
A clean sodium surface is illuminated with monochromatic light of various frequencies. The stopping potentials required to halt the emitted photoelectrons are measured as follows: Frequency : 4.6 5.0 5.4 5.8 Stopping potential : 0.2 0.8 1.3 1.9 (a) Describe how you would graph these data to reveal any linear relationship between stopping potential and frequency. Indicate which quantity should be placed on each axis. (b) Using the data, estimate (i) the threshold frequency for sodium and (ii) the constant of proportionality that relates to in the linear region. (c) Explain why a purely wave description of light that ties energy delivery only to intensity cannot account for the existence of the threshold frequency identified in part (b). (d) Discuss whether the photoelectric effect, as illustrated by these data, supports a wave description, a particle description, or a dual description of light. Provide two specific pieces of evidence to support your conclusion.Intuitive explanation
The photoelectric effect reveals a linear relationship between light frequency and electron kinetic energy. By plotting stopping potential against frequency, you can extract two key quantities: the work function (the minimum energy needed to free an electron) from the y-intercept, and Planck's constant from the slope. This is Einstein's photoelectric equation in action: the photon energy splits into work done against the surface and kinetic energy of the ejected electron.
Intuitive explanation
The photoelectric effect reveals a linear relationship between light frequency and electron kinetic energy. By plotting stopping potential against frequency, you can extract two key quantities: the work function (the minimum energy needed to free an electron) from the y-intercept, and Planck's constant from the slope. This is Einstein's photoelectric equation in action: the photon energy splits into work done against the surface and kinetic energy of the ejected electron.