De broglie wavelength and energy

[marpple]

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.. :(

 

[Redbelly98]

K is never equal to Uo.

What is the relation between K, U, and total energy E ?

 

[marpple]

k is never equal to uo.

What is the relation between k, u, and total energy e ?

e=k + u

 

[Redbelly98]

Okay. So what is K when 0 < x < L ?

 

[marpple]

okay. So what is k when 0 < x < l ?

k = e - u_0 = u_0 ?

 

[Redbelly98]

k = e - u_0 = u_0 ?

No.

The problem statement says E = ____ ?

 

[marpple]

No.

The problem statement says E = ____ ?

6 U_0

but, then i guess E = 6 U_0 is for K x > L

 

[Redbelly98]

E = 6 U_0 is for everywhere, all the time. Total energy is conserved, a constant, and never changes.

 

[marpple]

E = 6 U_0 is for everywhere, all the time. Total energy is conserved, a constant, and never changes.

yup.,, got it..
thanks :)