Schrodinger Equation Calculator
Calculate energy eigenvalues, wave functions, and quantum states for infinite wells and harmonic oscillators.
About this calculator
This calculator solves the time-independent Schrodinger equation for two standard textbook potentials, chosen via Potential Type. For the Infinite Square Well (a particle confined between impenetrable walls), Energy (Eₙ) follows Eₙ = n²π²ℏ²/(2mL²) -- it grows with the SQUARE of Quantum Number (n) and shrinks with the square of both Well Width / Char. Length (L) and Particle Mass (m), which is why quantum confinement effects only show up at atomic-scale widths. For the Harmonic Oscillator, the calculator treats Well Width / Char.
Length AS the oscillator's characteristic length x0, solving x0 = sqrt(ℏ/(mω)) backwards for angular frequency rather than asking for a spring constant directly, giving Eₙ = (n − 1/2)ℏω with Quantum Number (n) starting at 1 for the ground state -- matching the well's own n=1 convention rather than the oscillator's usual v=0 ground-state label. Number of Nodes always equals Quantum Number (n) − 1 in EITHER potential: the ground state (n=1) has zero nodes and each higher state adds exactly one, independent of Particle Mass or Well Width / Char. Length -- node count is a topological property of the wavefunction shape, not its energy. Wavelength (λₙ) and Momentum (pₙ) describe the particle's own de Broglie matter wave inside the well or oscillator, not a photon; Transition Frequency is instead the frequency of a photon that would be absorbed or emitted jumping to the next level, derived from Energy to Next Level.
Inputs
Results
Energy (Eₙ)
37.61 eV
Energy to Next Level
112.83 eV
Wavelength (λₙ)
0 m
How to Use This Calculator
- Enter Quantum Number (n): 1 is the ground state, higher values give excited states with more nodes.
- Select Potential Type: Infinite Square Well (particle in a box) or Harmonic Oscillator (equally spaced levels).
- Enter Well Width / Characteristic Length (m): atomic wells are ~1e-10 m (1 Å); quantum dots are ~10–100 nm.
- Set Particle Mass (kg): default is the electron mass (9.109e-31 kg).
- Read Energy (Eₙ) in eV, Wavelength (λₙ), and Number of Nodes — the ground state has zero nodes, n-th state has n−1 nodes.
How the result changes with Well Width / Char. Length
| Well Width / Char. Length | Energy (Eₙ) | Energy to Next Level | Wavelength (λₙ) |
|---|---|---|---|
| 0 | 150.44 eV | 451.33 eV | 0 m |
| 0 | 66.86 eV | 200.59 eV | 0 m |
| 0 | 16.72 eV | 50.15 eV | 0 m |
| 0 | 6.02 eV | 18.05 eV | 0 m |
What each input means
- Quantum Number (n)
- Principal quantum number
- Potential Type
- Type of confining potential
- Well Width / Char. Length
- Width of well or characteristic length
- Particle Mass
- Mass of the particle (default: electron)
What each result means
- Probability Density at Center
- Probability density |ψ(L/2)|² at the well's midpoint (infinite square well only; 0 for the harmonic oscillator, which this calculator does not compute separately).
How this is calculated
Formula
Eₙ = n²π²ℏ² / (2mL²)Worked example, using the default values
- Identify Input Parameters4 parametersQuantum Number (n) = 1, Potential Type = 0, Well Width / Char. Length = 1e-10, Particle Mass = 9.109e-31 = 4 input(s) provided
- Calculate EnergyEnergy = Number(energyEV.toExponential(4))37.611 = 37.611
- Calculate Energy to Next LevelEnergy to Next Level = Number(energySpacing.toExponential(4))112.83 = 112.83
- Calculate WavelengthWavelength = Number(wavelength.toExponential(3))2e-10 = 2e-10
- Calculate MomentumMomentum = Number(momentum.toExponential(3))3.313e-24 = 3.313e-24
- Calculate Transition FrequencyTransition Frequency = Number(transitionFrequency.toExponential(3))27280000000000000 = 27280000000000000
- Calculate Probability Density at CenterProbability Density at Center = (2/L) x sin²(nπ/2)20000000000 = 20000000000
Engine last updated . Checked against 6 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does raising Particle Mass always lower Energy (Eₙ), in both potential types?
Both formulas put mass in the denominator: the infinite well's Eₙ = n²π²ℏ²/(2mL²) and the harmonic oscillator's Eₙ = (n − 1/2)ℏω (where ω itself is inversely proportional to mass through ω = ℏ/(mL²)) both shrink as Particle Mass grows. Physically, a heavier particle needs less kinetic energy to have the same de Broglie wavelength fit inside the same confinement, so its quantized energy levels sit closer together and lower overall.
Why does Number of Nodes only depend on Quantum Number (n), not Particle Mass or Well Width?
Number of Nodes counts how many times the wavefunction crosses zero inside the well or oscillator, and that count is a purely topological property of the quantum state -- the ground state (n=1) always has zero nodes and every higher state adds exactly one, in both potentials modeled here. Particle Mass and Well Width / Char. Length change the ENERGY of each level, not how many times its wavefunction oscillates.
What does the Harmonic Oscillator branch do with Well Width / Char. Length, since there's no spring-constant input?
It reuses that field as the oscillator's characteristic length x0, and solves the standard relation x0 = sqrt(ℏ/(mω)) backwards for angular frequency ω, instead of asking for a spring constant directly. This keeps the same two physical inputs -- mass and a length -- meaningful across both potential types, at the cost of not letting you set stiffness and mass independently the way a real spring-mass system would.
Why does Quantum Number (n) start at 1 for the harmonic oscillator instead of the usual n=0 ground state?
This calculator keeps one Quantum Number (n) input that starts at 1 for BOTH potential types, so the harmonic oscillator branch computes energy as (n − 1/2)ℏω rather than the textbook (v + 1/2)ℏω with v starting at 0. Entering n=1 still gives the true ground-state energy of ℏω/2 -- it's labeled with the well's n=1 convention instead of the oscillator's own v=0 convention, so the two branches share one input scale.
Is Wavelength (λₙ) the color of light this system would emit?
No -- Wavelength (λₙ) is the particle's own de Broglie matter wavelength at that energy level, not a photon's wavelength. The photon emitted or absorbed in a transition between levels is described instead by Transition Frequency, which this calculator derives from Energy to Next Level rather than reporting a separate photon wavelength.
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