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Homework Help: What is the wavelength of an electron of 5eV energy?

  1. Feb 10, 2016 #1
    1. The problem statement, all variables and given/known data
    Calculate the wavelength of an electron which has 5eV of energy.

    2. Relevant equations
    de Broglie's equation: lambda=h/p , kinetic energy equation: K=0.5mv^2

    3. The attempt at a solution
    My attempt: I figured out that using de Broglie's wavelength equation was necessary for this question. but after changing around everything to get lambda = h/(2mK)^1/2, I kept on getting an incorrect answer.
    From comparing my methods to others I found that using Planck's constant's value in eV didn't work.
    What I really want to know is if I have to change the mass(m) to eV.
    The others had used Planck's constant's value in J/s and had multiplied the 2mK by the electron charge ( to change J/s to eV), and it had worked for them.
    Why is this?
  2. jcsd
  3. Feb 10, 2016 #2
    Take care with your units.
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