# Quantum Question

DarkKnight911

## Homework Statement

Light with a wavelength 600 nm is directed at a mettalic surface with a work function of 1.6 eV. A retarding potential of 0.5 V is applied. Determine:
a) The maximum kinetic energy, in joules, of an emitted electron before the retarding potential is applied.
b) The maximum speed with which an electron reaches the far side after the retarding potential is applied.

## Homework Equations

[/B]
Kinetic Energy = hf - w

## The Attempt at a Solution

I used the above equation to figure out "a" but, I do not know where to begin question "b."

Homework Helper
Welcome to PF!

The energy of the electron is conserved during its flight. Retarding potential means that it travels toward an electrode at negative potential with respect to the metallic surface. How much does the potential energy of the electron change?

DarkKnight911
Oh I see but can you please do it for me I just want a solid example to follow in the future.

Homework Helper
Oh I see but can you please do it for me I just want a solid example to follow in the future.
I can not do it for you, the rules of the Forums forbid it. We only can lead you.

Do you know what is the potential energy of a charge q at a point with potential U?