# Quantum Physics: Work Function and Electric Potential

JohnGaltis

## Homework Statement

Metal Surface is illuminated with 200nm wavelength light. Work Function of this metal is 3.0eV and its electric potential is 5V lower than a point of infinity.

Determine max K.E of photoelectrons, which are just emitted from the work surface.

## Homework Equations

K.Emax= hf - Φ
f=c/λ
Not sure what other equations.

## The Attempt at a Solution

I found f first by using f=c/λ. This way, I got a value of max K.E. But it's a really high mark question so it got to be more than just subbing in values.

I think I haven't yet include the impact the electric potential would have on the photoelectrons. It would cause the max K.E of photoelectrons to increase, right? Since it would be attracted to the metal surface and would need more energy to escape.

What equation would allow me to find the energy required to escape the surface?

## Answers and Replies

Let'sthink
Show your calculations. did you convert eV into joules?