# Photoelectric effect units

• struggles

## Homework Statement

In a photoelectric experiment, a stopping potential of 2.70 eV is measured when ultraviolet light of wavelength 380 nm is incident on the metal. If blue light of wavelength 440 nm is used, what is the new stopping potential in eV?

## The Attempt at a Solution

I think i understand how to do this problem (qV = hc/λ - work function) but am very confused as they have given and ask for the stopping potential in eV. I thought that eV was a unit of energy and that stopping potential (as it is a voltage) is given by the units V. How can the units of a potential be eV?

You're right. The stopping potential should really be measured in V, not eV. But since it is electrons you are stopping, people sometimes get sloppy and refer to electron energy (in eV) rather than the potential (in V).

So i should give the answer for the energy and not the potential?

The numerical results should be the same. I would five the answer in V, and explain that the question is really incorrect, since potentials are measured in V.

ok thank you very much!