(Part 2: Discussion)
Reflection Simulation: Read the question, the student response and the expert answer below, then critique the students
on how it compares to the expert's response following the prompts.
Question:
Describe how to obtain the work function of the metal from the fit you performed in the previous question and
discuss two tests based on your fit and plot to assess whether or not you would trust the value for the work function
you obtain.
Student Response:
We can get the work function from the intercept of the fit. To check if it is any good, we compare the Planck constant
we get from the fit to the real one, then also we can compare the value of the Planck constant in eV instead of in
Joules. If these match then we know the work function is also reliable since the fit is proven to be a good one.
Expert answer:
The y-intercept of the fit is the work function of the metal in eV, or the work function in Joules divided by the charge
on the electron. To assess its potential correctness, we can compare our value for Planck's constant (obtained via
the gradient as in question one) to the known value. If these agree within 3 standard uncertainties, then we can gain
some confidence in our results. We can further boost our confidence by comparing the line of best fit to the data
points. Looking at the error bars on each point if the fit passes through these for each point (or really within three
error bar lengths from each point) then we are even more confident in our fit describing the results well and hence in
the intercept giving a correct result for the work function.
Your critique:
Q2. How does the student's answer compare to the expert's? Did the student describe in detail how to extract the valu
of the work function? Has the student provided two unique, clearly described, and justified means of checking the
validity of the work function obtained?
