Quick question on calculating wavelength.

[lyrebird]

Homework Statement

Light strikes a sodium surface, causing photoelectric emission. The stopping potential for the ejected electrons is 4.6 V, and the work function of sodium is 2.2 eV. What is the wavelength of the incident light?

Homework Equations

The Attempt at a Solution

Problem solved, thanks. :)

 

[Stonebridge]

The equation E=hf for the energy of a photon of frequency f, will give energy in joules. (if h is in SI units)
So the work function and maximum ke of electrons (given by the stopping potential) also need to be in joules.

 

[lyrebird]

The equation E=hf for the energy of a photon of frequency f, will give energy in joules. (if h is in SI units)
So the work function and maximum ke of electrons (given by the stopping potential) also need to be in joules.

To calculate the maximum kinetic energy, I would just multiply the charge on an electron by the stopping potential 4.6V, wouldn't I?

 

[Stonebridge]

To calculate the maximum kinetic energy, I would just multiply the charge on an electron by the stopping potential 4.6V, wouldn't I?

Yes. That's correct. It's the same idea as calculating the k.e. an electron gains when accelerating through a potential V. The only difference here is that the electric field acts to decelerate the electron rather than accelerate it.