1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

De Broglie Formula Application

  1. May 6, 2009 #1
    1. The problem statement, all variables and given/known data
    Estimate the wavelength of a 30 keV electron.

    2. Relevant equations
    p = h/λ
    E = hf

    3. The attempt at a solution
    The electron has 30 keV of mass-energy.
    As it is acting as a particle-wave, E = hf, so f = E/h = 30,000x1.6x10^-19/6.3X10^-34 = 7.619x10^18 Hz

    Now, v = fλ, so λ = v/f, but this is where I run into a problem, as I'm not told what speed the electron is travelling at - do I assume speed of light, or is there some other way?
  2. jcsd
  3. May 6, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi Pyroadept! :smile:

    If you can convert the eV into J, and if you know the mass of an electron, then you can calculate the speed from the energy. :wink:
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Broglie Formula Application Date
De – Broglie wavelength of O_2 Dec 26, 2017
E = hf Mar 20, 2017
De Broglie wavelength and energy levels Aug 30, 2016
Double-slit experiment: What is the speed of the neutrons? May 8, 2016
Energy of a proton using de broglie formula Aug 18, 2010