Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Absorbed photons, emmited photons

  1. Feb 19, 2009 #1
    1. The problem statement, all variables and given/known data

    how can i tell if a photon is being emmited or absorbed?

    2. Relevant equations

    hc/lambda= energy per photon

    3. The attempt at a solution

    photons are absorbed when the energy of the photon= energy of transition?
    when are they emmited?
    and i thought that energy of photon was always = to energy of transition so im a bit confused.
    for example, A photon with λ = 600 nm interacts with a hydrogen atom in fundamental state is the photon absorbed? how can i see whether it is or not?
    i know fundamental state is k=1 but i dont know how i can see whether it is being absorbed or not
  2. jcsd
  3. Feb 19, 2009 #2

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    That's an easy one: When a photon is absorbed it promotes the atom to a higher energy state. So absorption takes place when the final state is higher than the initial state. When a photon is emitted it is a de-excitation of the atom. That is, the atom goes from a higher state to a lower state.

    If the initial state is k=1 then the only thing the atom can do is absorb a photon. It can't de-excite to a lower energy level because there's nowhere for it to go.
  4. Feb 19, 2009 #3
    o ok.
    but if k=1 and i get n=1.08 and since only integers are accepted would it round off to 1 and not absorb? or since it is a larger number than 1 it would absorb?

    if it absorbs, would the rest of the energy that was left that didnt absorb turn into kinetic energy?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook