How do you solve for multiple constants given the wave functions at the boundary?

In summary, solving for multiple constants given wave functions at the boundary involves applying boundary conditions to the wave equations. This typically requires substituting known values of the wave functions and their derivatives at the boundaries into the equations. By creating a system of equations based on these conditions, the constants can be isolated and solved simultaneously. Techniques such as linear algebra or matrix methods may be employed to streamline the process, ensuring the constants satisfy both the boundary conditions and the wave equations throughout the domain.
  • #1
Danielk010
34
4
Homework Statement
In the region 0 ≤ x ≤ a, a particle is described by
the wave function ψ1(x) = ##−b(x^2 − a^2 )##. In the region
a ≤ x ≤ w, its wave function is ψ2(x) = ##(x − d)^2 − c##. For
x ≥ w, ψ3(x) = 0. (a) By applying the continuity conditions
at x = a, find c and d in terms of a and b. (b) Find w in terms of
a and b.
Relevant Equations
ψ1(x) = ##−b(x^2 − a^2 )##. 0 ≤ x ≤ a
ψ2(x) = ##(x − d)^2 − c##. a ≤ x ≤ w
ψ3(x) = 0 x ≥ w
From my understanding, you can equate ψ1(x) and ψ2(x) at the boundary of x = a, so I plugged in the values of a into x for both equations and I got ψ1(x) = 0 and ψ2(x) = ## (a-d)^2-c ##. I am a bit stuck on where to go from here.
 
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  • #2
Danielk010 said:
and I got ψ1(x) = 0 and ψ2(x) = ## (a-d)^2-c ##. I am a bit stuck on where to go from here.
No. You got ψ1(a) = 0 and ψ2(a) = ## (a-d)^2-c ##. Equating ψ1 and ψ2 at x=a means you have ψ1(a) = ψ2(a)

Then: what about continuity of the first derivative ?

##\ ##
 
  • #3
BvU said:
No. You got ψ1(a) = 0 and ψ2(a) = ## (a-d)^2-c ##. Equating ψ1 and ψ2 at x=a means you have ψ1(a) = ψ2(a)

Then: what about continuity of the first derivative ?

##\ ##
The continuity for the first derivative of which wave function?
 
  • #4
BvU said:
No. You got ψ1(a) = 0 and ψ2(a) = ## (a-d)^2-c ##. Equating ψ1 and ψ2 at x=a means you have ψ1(a) = ψ2(a)

Then: what about continuity of the first derivative ?

##\ ##
I got it. Thank you so much for the help
 
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FAQ: How do you solve for multiple constants given the wave functions at the boundary?

What are wave functions and why are they important in solving for constants?

Wave functions describe the quantum state of a system and contain all the information about the system's behavior. They are essential in quantum mechanics because they help predict the probabilities of finding a particle in various states. Solving for constants in wave functions is crucial for ensuring that the solutions meet specific physical conditions, such as boundary conditions, which are necessary for accurate modeling of quantum systems.

What are boundary conditions in the context of wave functions?

Boundary conditions are constraints that the wave function must satisfy at the edges of the domain under consideration. They can be specified in various forms, such as Dirichlet conditions (where the wave function takes specific values), Neumann conditions (where the derivative of the wave function is specified), or mixed conditions. These conditions are critical for determining the allowed energy levels and the corresponding wave functions of a quantum system.

How do you set up equations to solve for multiple constants?

To solve for multiple constants, you typically start by writing the general form of the wave function that satisfies the system's differential equation. Next, you apply the boundary conditions to generate a set of equations. These equations will often involve the constants you need to solve for. By substituting the boundary conditions into the general wave function, you can create a system of linear equations that can be solved using algebraic methods.

What methods can be used to solve the resulting equations for constants?

Several methods can be employed to solve the equations for constants, including substitution, elimination, and matrix methods. For larger systems, numerical methods such as the finite difference method or the finite element method may be used to approximate solutions. In many cases, software tools like MATLAB or Mathematica can assist in solving complex systems of equations efficiently.

What are common challenges faced when solving for constants in wave functions?

Common challenges include dealing with non-linear equations, ensuring that the boundary conditions are correctly applied, and managing the complexity of the system as the number of constants increases. Additionally, ensuring that the solutions are physically meaningful and normalized can also pose difficulties. Careful mathematical manipulation and sometimes iterative approaches may be necessary to overcome these challenges.

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