Respuesta :
Answer:
φ = √2/L sin (kx), E = (h² / 8 mL²) n²
Explanation:
The Schrödinger equation for a particle in a box is, described by a particle within a potential for simplicity with infinite barrier
V (x) = ∞ x <0
0 0 <x <L
∞ x> L
This means that we have a box of length L
We write the equation
(- h’² /2m d² / dx² + V) φ = E φ
h’= h / 2π
The region of interest is inside the box, since being the infinite potential there can be no solutions outside the box. The potential is zero
- h’² /2m d²φ/ dx² = E φ
The solution for this equation is a sine wave,
Because it is easier to work with exponentials, let's use the reaction between the sine function and cook with the exponential
[tex]e^{ikx}[/tex] = cos kx + i sin kx
Let's make derivatives
dφ / dx = ika e^{ikx}
d²φ / dx² = (ik) e^{ikx} = - k² e^{ikx}
Let's replace
- h'² / 2m (-k² e^{ikx}) = E e^{ikx}
E = h'² / 2m k²
To have a solution this expression
Now let's work on the wave function, as it is a second degree differential bond, two solutions must be taken
φ = A e^{ikx} + B e^{-ikx}
This is a wave that moves to the right and the other to the left.
Let's impose border conditions
φ (0) = 0
φ (L) = 0
For being the infinite potential
With the first border condition
0 = A + B
A = -B
They are the second condition
0 = A e^{ikL}+ B e^{-ikL}
We replace
0 = A (e^{ikL} - e^{-ikL})
We multiply and divide by 2i, to use the relationship
sin kx = (e^{ikx} - e^{-ikx}) / i2
0 = A 2i sin kL
Therefore kL = nπ
k = nπ / L
The solution remains
φ = A sin (kx)
E = (h² / 8 mL²) n²
To find the constant A we must normalize the wave function
φ*φ = 1
A² ∫ sin² kx dx = 1
We change the variable
sin² kx = ½ (1 - cos 2kx)
A =√ 2 / L
The definitive function is
φ = √2/L sin (kx)
