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Calculate the wavelength of electrons traveling at 1.15x10^5

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  1. Apr 26, 2015 #1
    1. The problem statement, all variables and given/known data
    Calculate the wavelength of electrons traveling at 1.15x10^5 m/s

    2. Relevant equations
    λ = h/m*v

    Given values:
    h=6.626x10^-34 J*s
    m=9.11x10^-31kg
    v=1.15x10^5 m/s

    3. The attempt at a solution
    I converted J*s to SI units (kg⋅m2⋅s−2) and then substituted out all known values, to get:
    λ = (6.626x10^-34 kg⋅m2⋅s−2)/(9.11x10^-31kg)(1.15x10^5 m/s)

    After canceling out like units and doing the math, I get:
    λ = 6.00x10^-9m

    The text gives the solution as 6.33nm. I can't figure out how they got there (and why they converted to nm?).

    Is this an error in the text or (more likely) in my logic/calcuations?

    Any/all input is appreciated. Thanks!
     
  2. jcsd
  3. Apr 26, 2015 #2

    Doc Al

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    Staff: Mentor

    Your expression is correct, just redo the arithmetic. For wavelengths that small, nm is a typical unit.
     
  4. Apr 26, 2015 #3
    Ah, good to know about nm... And I'll do the math again (hopefully better!). Thanks :)
     
  5. May 16, 2015 #4

    James Pelezo

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    Gold Member

    If interested, and using the wavelength determined in the above problem, calculate the amount of energy in 1 gram of electrons moving at the same speed. (See if you can get ∆E = 1.9 x 104Kj/mole e-'s = 3.45 x 107Kj/g e-'s. Compare: A candle flame generating q ~ 40.7 Kj/g from burning paraffin wax to the energy content of a gram of electrons traveling at 1.15 x 105m/s. => You might find it very surprising. You are definitely on the right track. Good job!
     
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