Calculate De Broglie Wavelength of Electron | Help for Final Exam

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SUMMARY

The discussion focuses on calculating the De Broglie wavelength of an electron with a kinetic energy (KE) of 40 eV. The initial calculation yielded a wavelength of 3.9 x 10^-10 m, which was identified as incorrect due to a misunderstanding of the formulas involved. The correct approach requires using the relationship between kinetic energy, momentum, and wavelength, specifically noting that the answer should be halved, leading to a wavelength of approximately 1.85 x 10^-10 m. Participants emphasized the importance of showing work to identify errors in calculations.

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  • Understanding of kinetic energy in electron volts (eV)
  • Familiarity with De Broglie wavelength formula
  • Knowledge of momentum and its relation to mass and velocity
  • Basic algebra for manipulating equations
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  • Practice problems involving kinetic energy calculations in quantum mechanics
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Students preparing for physics exams, particularly those studying quantum mechanics and wave-particle duality, as well as educators seeking to clarify concepts related to the De Broglie wavelength.

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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