(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

In an advanced laboratory class a student performs the photoelectric experiment. Ultraviolet light is shone on a particular metal and the stopping potential is measured at the same time. It is found that 2.61 V is needed to stop all the electrons when the wavelength of the light is 285 nm, and 4.53 V for a wavelength of 207 nm. What is the work function of the metal?

2. Relevant equations

[tex]hf=eV+\phi[/tex]

Find [tex]\phi[/tex]

3. The attempt at a solution

(1)[tex]hf_{1}=eV_{1}+\phi[/tex]

(2)[tex]hf_{2}=eV_{2}+\phi[/tex]

divide 1 by 2 to get rid of h, and we get

[tex]\frac{f_{1}}{f_{2}}=\frac{eV_{1}+\phi}{eV_{2}+\phi}[/tex]

i can't seem to solve for [tex]\phi[/tex] and get the correct answer. i've tried doing it both algebraically(sp, sry) and with a calculator. possibly i'm putting the numbers in wrong? i have:

[tex]e=1.6022*10^-19 C[/tex]

[tex]f_{1}=285*10^-9 m[/tex]

[tex]f_{2}=207*10^-9 m[/tex]

[tex]V_{1}=2.61V[/tex]

[tex]V_{2}=4.53V[/tex]

where am i going wrong? please help

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Planck's Constant measured in photoelectric effect

**Physics Forums | Science Articles, Homework Help, Discussion**