Chemistry

[nikki_piper]

What effect does the color of the light have on the release of electrons from a sodium metal surface?

(a) Write a brief experimental design to answer this question
(b) Would you expect all the colors of light to release electrons from the sodium metal? Justify your answer using the idea of photons.

I think it has something to do with Bohr and photons, as well as the frequency and intensity of the light?? I don't know where to start. IThis assignement is due tommorow and i'm completely confused. Can somebody please help me???
Thank You!

[jake-the-peg]

Oooh great question

This is the photo-electric effect. Albert Einstein got his Nobel Prize for this one!

Basically when you shine light on the metal whether or not you get electrons knocked off does not depend on how strong the light is but on what colour (sorry color) it is!

Doesn't matter how strong the red light is - no electrons. Really weak blue light - you get electrons.

Here's a little applet demonstrating it:
http://www.lon-capa.org/~mmp/kap28/PhotoEffect /photo.htm

It's because light is bundled up into little parcels of energy called photons and the energy of a photon depends on it's wavelength.

You can't knock an electron out with 5 or 6 electrons working together there has to be enough energy in 1 photon to do the job - that's why the color is important.

There's a bit on this on one of my favorite science teaching sites here:
http://www.colorado.edu/physics/2000/quantumzo ne/photoelectric.html

If you're still stuck google photoelectric effect

[Teddio]

The photon energy must exceed the Work Function of the metal. Photon energy increases as the wavelength of the light (electromagnetic radiation) decreases.