Natural Science Forum / Physics / Particle Physics / March 2007

Hello,

I am trying to understand the following statement on photoelectric
effect:

"When light shines on a metal, electrons are emitted. However,
electrons are emitted only at specifc threshold frequency."

I am guess the experimental setup is something as follows:

1. Shine light on a metal.
2. Start at a specific frequency of light.
3. Keep on increasing the frequency of light.
4. At discrete frequencies, you will see (not by naked eyes) eletrons
being emitted.

I would appreciate it if someone can help me understand some
fundamentals:

1. How do you go about changing the frequency of light?
2. Who is losing the electrons? The metal or the light?
3. I guess the atom gets decomposed into electrons and protons. What
happens to the protons?
4. In theory, if light continues to shine on a metal at a specifc
frequency, in a few billion years, the metal will disappear as it
continues to lose atoms. Is this correct?
5. Finally, just because electrons are being emitted at specific
frequencies, how do you conclude that light has discrete particles of
energy?

Thank you in advance for your help.

Pete