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

Homework Help: Bohr's theory

  1. May 1, 2006 #1
    Hi guys, I'm hopelessly stuck on a couple of quantum questions. Any guidance would be very much appreciated!

    (1) According to Bohr's theory, what would be the four longest wavelengths of light that can be absorbed by a stationary hydrogen atom initially in its ground state? If an atom absorbs a photon with the longest of these wavelengths, with what velocity does it subsequently move? What is the longest wavelength of light that can ionize such an atom?

    (2) A hydrogen atom, initially at rest in the lab frame, in its ground state absorbs a photon with a frequency required to excite it to the first excited state. Calculate the recoil velocity of the atom due to the absorption process and show that the final kinetic energy of the atom is negligible.

    Best regards, James.
  2. jcsd
  3. May 2, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    See this reference on the hydrogen spectrum - http://hyperphysics.phy-astr.gsu.edu/Hbase/hyde.html#c4

    Transitions to and from the ground state are UV and the series are known as the Lyman series.

    Remember - light has momentum p = E/c and the hydrogen atom would have momentum p = mv.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook