1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Kinetic Enegry and Hydrogen Atoms

  1. Oct 30, 2014 #1
    1. The problem statement, all variables and given/known data

    (a) What is the minimum kinetic energy in electron volts that an electron must have to be able to ionize a hydrogen atom (that is, remove the electron from being bound to the proton)? Answer: 13.6 eV

    (b) If electrons of energy 12.8 eV are incident on a gas of hydrogen atoms in their ground state, what are the energies of the photons that are emitted by the excited gas?
    Energy of highest-energy photon: 12.8 eV
    Energy of next highest-energy photon: 12.089 eV
    Energy of next highest-energy photon: 10.2 eV
    Energy of next highest-energy photon: 2.6 eV
    Energy of next highest-energy photon: 1.9 eV
    Energy of lowest-energy photon: ?? eV

    (c) If instead of electrons, photons of all energies between 0 and 12.8 eV are incident on a gas of hydrogen atoms in their ground state, what are the energies at which the photons are absorbed?
    Energy of highest-energy dark line: 12.8 eV
    Energy of next highest-energy dark line: 12.089 eV
    Energy of lowest-energy dark line: 10.2 eV

    2. Relevant equations

    -13.6/n2

    3. The attempt at a solution

    I thought you would take 12.8-12.089 = .711 eV, however it states this is wrong. I have tried answers 0, .7, .711, and .6. Not sure why it's wrong.
     
  2. jcsd
  3. Oct 30, 2014 #2

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    OK - so how was the highest energy photon generated?
     
  4. Oct 30, 2014 #3
    Due to the fact that the questions says 12.8eV is the ground state, wouldn't that result in 12.8 being the highest energy photon?
     
  5. Oct 30, 2014 #4

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    The question does not say that 12.8eV is the ground state.
    What is the ground state energy of a hydrogen atom?

    But you didn;t answer the question: what is the mechanism that generates the photons?

    BTW: are those numbers given to you are did you work them out?
     
  6. Oct 30, 2014 #5
    En=K+Ue=-13.6eV/N2

    -13.6/No2+13.6=12.8

    No2= -13.6/0.8= -17
    √(17) ≈ 4

    -13.6/42+13.6=12.75
     
  7. Oct 30, 2014 #6
    I worked them out.
     
  8. Oct 30, 2014 #7

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    That's just a bunch of equations - please use English to explain what you are doing.
    What is the physical process you are thinking of ... an electron flies through the gas, it encounters a H atom, and then what does it do?
     
  9. Oct 30, 2014 #8
    I have know idea...I am using the equations that were given in class.
     
  10. Oct 30, 2014 #9
    I solved it.

    -13.6/42+13.6/32=.66
     
  11. Oct 31, 2014 #10

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Well great - but I have no idea what you did because you have not used an physics.
    It sounds like you don't know either. This does not bode well for the future - when there will be no equations given in class.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Kinetic Enegry and Hydrogen Atoms
  1. Hydrogen atom (Replies: 3)

  2. Hydrogen atom (Replies: 1)

Loading...