Question

Sodium metal used in photoelectric experiment, illuminated with light wavelength 420nm. Stopping potential is .65volts. a. What is sodium's work function? b. What wavelength would produce a stopping potential of 1.69V with the same setup?

Answer 1

According to wikipedia:

The maximum kinetic energy of an ejected electron is given by


where h is the Planck constant and f is the frequency of the incident photon. The term is the work function (sometimes denoted ), which gives the minimum energy required to remove a delocalised electron from the surface of the metal.

With stopping voltage Kmax = e(Vstopping)

So can't you just use the velocity of light (which I'm assuming is the speed of light) and the wavelength given to figure out the frequency, and then that frequency multiplied by plank's constant would give you the value equal to this "work function"?