PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
In an experiment, a student measures the stopping potential Vs needed to halt photoelectrons ejected from an unknown metal when it is exposed to two different monochromatic light sources. The data are summarized below.
Trial
Frequency of Light f (×10¹⁴ Hz)
Stopping Potential Vs (V)
1
5.2
0.60
2
6.0
2.40
Assume the electron charge magnitude is e.
(a) Using only the two data points provided, determine an experimental value for Planck’s constant h in joule-seconds. Show all steps in your calculation.
(b) From the same data, calculate the work function ϕ of the metal in electron-volts.
(c) A third light source of frequency 7.0×1014Hz is directed onto the same metal surface. Predict the expected stopping potential and explain how you obtained your result.
(d) Discuss two possible sources of systematic error in this experiment that could cause the calculated value of h to deviate from the accepted value.