# Photoelectric Effect and stopping potential

1. Sep 9, 2013

### Turion

1. The problem statement, all variables and given/known data

When 445 nm light strikes a certain metal surface, the stopping potential is 70% of that which results when 410 nm light strikes the same metal.

2. Relevant equations

3. The attempt at a solution

$$P=0.7P'\\ \frac { nE }{ t } =\frac { 0.7nE' }{ t } \\ \frac { hc }{ λ } =\frac { 0.7hc }{ λ' } \\ \frac { λ' }{ λ } =0.7$$

2. Sep 9, 2013

### Enigman

And the question is???
Oh and you are neglecting the work function of the metal- I think

3. Sep 11, 2013

### Turion

Opps. I didn't realize the question was cut off.

Here's the second part:

Based on this information and the table given in the textbook, identify the metal.

Basically, what is required is to calculate the work function.

A: work function 2.23 eV. Potassium.

4. Sep 14, 2013

### Saitama

Show your effort please. As suggested, did you take the work function into account? Retry the problem.