Calculate De Broglie Wavelength of Electron | Help for Final Exam

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Discussion Overview

The discussion revolves around calculating the De Broglie wavelength of an electron with a kinetic energy of 40 eV. Participants are seeking assistance with the problem, which is related to homework and exam preparation in quantum mechanics.

Discussion Character

  • Homework-related, Mathematical reasoning

Main Points Raised

  • One participant presents an initial calculation of the De Broglie wavelength as 3.9 x 10^-10 m but expresses uncertainty about its correctness.
  • Another participant references a source suggesting that the wavelength should be half of the initial calculation, prompting a check of the equations used.
  • A third participant emphasizes the need to use two specific formulas: one relating kinetic energy to momentum and mass, and another relating momentum to wavelength, suggesting a potential error in the initial calculation.
  • A fourth participant proposes a different value of 1.85079 x 10^-25 m based solely on the input of the kinetic energy, without considering mass or velocity.
  • Another participant requests to see the calculations to better understand the discrepancies in the answers provided.

Areas of Agreement / Disagreement

There is no consensus on the correct answer, as participants present differing calculations and interpretations of the formulas involved. The discussion remains unresolved regarding the accurate value of the De Broglie wavelength.

Contextual Notes

Participants have not fully detailed their assumptions or the steps taken in their calculations, leading to uncertainty about the correctness of the values presented. There is also a lack of clarity on the definitions and parameters used in the calculations.

sharpielife
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I'm reviewing for one of my final exam and I can't seem to figure out this problem:

Find the Debroglie wavelength of an electron with a KE of 40 ev.

I got an answer of 3.9 x 10^-10 m.

I keep getting it wrong and I'm not sure what to do.
Thanks in advance!
 
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You should only be using two formulas. One involves KE in terms of momentum and mass, and the other relates momentum and wavelength. Your answer is off by a factor of 1/2 so I'm guessing that you are making some mistake in your math.

So why don't you show us what you've done?
 
Hmm according to the hyperphysics website, my answer should have been
1.85079 x 10 ^ -25

would that be right?
All i did was input the ev value of 40, but I did not input anything for mass or velocity.
 
Why don't you show us your work? Your answer is not right yet, you were closer the first time. Mind you that this thread should be at the homework help section.
 

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