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De broglie wavelength and energy

  • Thread starter marpple
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  • #1
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Homework Statement


The potential-energy function U(x) has the constant value U_0 in the interval 0 < x < L and is zero outside this interval. An electron is moving past this square barrier, but the energy of the electron is greater than the barrier height.

If E= 6 U_0, what is the ratio of the de Broglie wavelength of the electron in the region x > L to the wavelength for 0 < x < L?

Homework Equations



λ=h/p= h/ sqrt(2mK)

The Attempt at a Solution



K are for x>L and K are for 0<x<L

lamda1 / lambda 2 = sqrt(K2) / sqrt (K1) = sqrt (U_0) / sqrt (6U_0) = 1/ sqrt(6)

anyone.. please help me to spot the mistakes.. :(
 

Answers and Replies

  • #2
Redbelly98
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K is never equal to Uo.

What is the relation between K, U, and total energy E ?
 
  • #3
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k is never equal to uo.

What is the relation between k, u, and total energy e ?
e=k + u
 
  • #4
Redbelly98
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Okay. So what is K when 0 < x < L ?
 
  • #5
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okay. So what is k when 0 < x < l ?
k = e - u_0 = u_0 ????
 
  • #6
Redbelly98
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k = e - u_0 = u_0 ????
No.

The problem statement says E = ____ ?
 
  • #7
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No.

The problem statement says E = ____ ?
6 U_0

but, then i guess E = 6 U_0 is for K x > L
 
  • #8
Redbelly98
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E = 6 U_0 is for everywhere, all the time. Total energy is conserved, a constant, and never changes.
 
  • #9
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E = 6 U_0 is for everywhere, all the time. Total energy is conserved, a constant, and never changes.
yup.,, got it..
thanks :)
 

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