# Photoelectric effect and current

solars
In a photoelectric effect experiment, which of the following changes by result in a current, if there was no current flowing previously?

1. decreasing voltage in apparatus
2. decreasing frequency of the incident light
3. making the incident light brighter
4. increasing wavelength of the incident light
5. making the color of the incident light bluer

So I've done some research and I came across the fact that "Larger radiation intensity or frequency would produce more current."

source: http://en.wikipedia.org/wiki/Photoelectric_effect

So I've narrowed down the answer choices to 3 and 5. but not sure which one is right. can someone help me? thanks.

## Answers and Replies

cryptoguy
What you say about larger intensity/frequency is absolutely right. Take a look at the electromagnetic spectrum. If you're making the light bluer are you increasing the frequency or decreasing it?

Homework Helper
There's actually a lot of difference between something changing from zero photoelectric current flow to some current flow and some current flow to larger current. Just think about why there may be zero current flow in the first place.

solars
What you say about larger intensity/frequency is absolutely right. Take a look at the electromagnetic spectrum. If you're making the light bluer are you increasing the frequency or decreasing it?

I looked at the electromagnetic spectrum. By bluer does it mean a darker blue, if so the wavelenght decreases so frequency increases. But the other choice says making the light brighter does that mean increasing intensity or just making it go for let's say blue to yellow?

solars
There's actually a lot of difference between something changing from zero photoelectric current flow to some current flow and some current flow to larger current. Just think about why there may be zero current flow in the first place.

I don't know the reason why, but I have learned of something called the stopping voltage?

Homework Helper
It may be due to more than one factor, and I suspect that your original question may either be poorly worded or there is more than 1 answer.

cryptoguy
If there was NO current flowing at a certain frequency of light, it doesn't matter how intense the light beam is, no current will flow (because no electrons are excited).