Question

How does the wavelength of light affect the photoelectric current?

Answer 1

@gerryliyana ...

Answer 2

if wavelenght is less photoelectric current is high

Answer 3

Gerryliyana wanted to chat about this from a paper he put up a while back, he has disappeared...!

Answer 4

@gerryliyana - you have 10 minutes?

Answer 5

i'm sorry @furnessj , my connection is poor..,

yes of course..., if wavelength is increase, quantum energy of the photon and photoelectric current is decrease., right?

Answer 6

yes i have

Answer 7

Hi!
yes, you have that right.

Answer 8

So those papers, were scientists doing experiments where they varied the wavelength carefully and measured the current they got. They found that a specific wavelength gave the best current for a given metal (sodium in this case). So the previous statement doesn't _always_ hold (that the current increases for lower wavelengths).

Answer 9

ohh , then?

Answer 10

Have a play with this, it is excellent.

http://phet.colorado.edu/en/simulation/photoelectric

Tick the box for the current vs intensity graph. then adjust the COLOUR of the light (wavelength). You will see that at red, you get no current, then once you pass the threshold frequency, current increases up to a maximum, but then falls to zero again as the wavelength gets very short. It does their exxperiment on you computer! (You will see the peak like in their graph).

Answer 11

And finally, they remark about how sensitive it is, as hardly ANY light intesity is required to get measurable current. In the second paper, they go on to explain the advantages of this, and describe how this technique be used as a 'detector' which is superior to a human eye in optics experiments

Answer 12

very nice,

so alkali metals has a sensibility for different colors? how high the sensibility of alkali metal compared to other metals?

Answer 13

First question:
Well, I would say all metals have a sensibility to different colours.. specifically though they definitely have a threshold frequency. As you increase the frequency further, the current does increase, as electrons requiring MORE than the work function are ALSO released. However increasing the energy further and further does not get you more and more electrons (current), I presume because the wavelengths no longer 'interact' with the electrons/atoms.

Answer 14

Second question:
First, I think this question may not be needed now..? I don't really know if the sensitivity to colour is higher in different metals. I guess it would require an experiment with data that showed changing profiles (i'll draw an example below - here I 'pretend' that sodium is more sensitive than zinc).

In terms of 'energy' required to get a current, alkali metals certainly need less than other 'stable' metals. The outer electrons are easier to remove in alkali metals, they require a smaller ionization energy, so a lower frequency photon. Try out the different metals on that simulation..