If an incident photon with frequency f hits a metal with a work force of w: How do I find the color of the incident photon and the threshold frequency of the metal?

What equations are necessary to find the color and threshold frequency?

Is there an easy explanation for this?

  • $\begingroup$ A quick google search, and wikipedia read would probably be quite fruitful. $\endgroup$ Apr 28, 2013 at 0:57
  • $\begingroup$ @zhermes - I've been searching for an hour and I have no idea how to find the frequency of metal, only the frequency of a photon. $\endgroup$
    – Genevieve
    Apr 28, 2013 at 1:05
  • 1
    $\begingroup$ The very first article in a google search is wikipedia's photoelectric effect. The article defines a metal's threshold frequency within roughly the first page. $\endgroup$ Apr 28, 2013 at 1:16

1 Answer 1


I think you should re-read the question, because "frequency of the metal" doesn't make much sense in this context. And the color of photon is dependant only on it's frequency which is given. Do you need some further explanations on that?

Photoeffect's main equation is one of energy balance. The only energy source in this event is the photon whose energy is $hf$. If that is enough to eject an electron ($\ge w$), the emission occurs. The leftover energy becomes kinetic energy of the electron. $$hf=w+K$$

The threshold is the case where you get just enough energy to emit the electron but no leftover. The needed equation is $$hf=w$$

  • $\begingroup$ I meant "threshold frequency of the metal" sorry. :( $\endgroup$
    – Genevieve
    Apr 27, 2013 at 23:07
  • $\begingroup$ Also, to find the color, I needed to find the wavelength in nm. $\endgroup$
    – Genevieve
    Apr 28, 2013 at 0:19
  • $\begingroup$ The equation for that is c/f = lambda $\endgroup$
    – Genevieve
    Apr 28, 2013 at 0:20
  • $\begingroup$ So you're saying that to find the threshold frequency of the metal, you have to divide w/h? $\endgroup$
    – Genevieve
    Apr 28, 2013 at 1:04
  • 1
    $\begingroup$ Yes, w/h is correct. $\endgroup$
    – Džuris
    Apr 28, 2013 at 10:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.