Students investigate a metal surface by illuminating it with monochromatic light of…
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
Students investigate a metal surface by illuminating it with monochromatic light of various frequencies. For each frequency they adjust a variable potential difference until the photoelectron current just falls to zero, and they record that potential difference as the stopping potential Vstop. Their data are shown in the table.
Frequency f(×1014Hz) : 5.0 , 5.5 , 6.0 , 6.5 , 7.0
Stopping potential Vstop (V) : 0.4 , 0.9 , 1.4 , 1.9 , 2.4
Use e=1.60×10−19C where needed.
(a) On your own axes, plot the stopping potential on the vertical axis versus frequency on the horizontal axis and draw the best-fit straight line through the data points.
(b) Determine the numerical value of the slope of your best-fit line and state its units.
(c) Use the slope to calculate a value for Planck’s constant.
(d) From your graph, determine the threshold frequency of the metal and use it to calculate the work function in electron-volts.