Question

A series of measurements were taken of the maximum kinetic energy of photoelectrons emitted from a metallic surface when light of various frequencies is incident on the surface.

a. The table below lists the measurements that were taken. On the axes below, plot the kinetic energy versus light frequency for the five data points given. Draw on the graph the line that is your estimate of the best straight-line fit to the data points

b. From this experiment, determine a value of Planck's constant h in units of electron volt-seconds. Briefly explain how you did this

Answer 1

(a)

b. From K = hf – φ which is an equation of form y = mx + b

It is clear that the slope is h.

Use points on the line to find the slope. Only one of the data points is on the line, so we have to choose an arbitrary second point on the line to find the slope such as (x = 9 x 10¹⁴, y = 1.6 eV). Using this point and the first data point we get

h = 3.75 x 10^–15 eV-s