Tunneling starts here as an exact finite model, not a material calculation. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A barrier can leave a nonzero tail

This toy model gives a transmitted probability of 1/4. That is not a real material constant; it is the declared exact model.

T=14T=\frac{1}{4}
Barrier with a tailThe transmitted probability is part of the toy model.R=3/4T=1/41/2tail P=1/4

The tail row is small but nonzero

The toy split shows reflected, transmitted, and total rows before any material claim is made.

partPclaimreflected34largertransmitted14nonzerototal1closed\begin{array}{c|c|c}\text{part}&P&\text{claim}\\\text{reflected}&\frac{3}{4}&\text{larger}\\\text{transmitted}&\frac{1}{4}&\text{nonzero}\\\text{total}&1&\text{closed}\\\end{array}
Nonzero-tail scanThe tail is a declared exact probability.R=3/4T=1/41/2tail P=1/4

The model is finite and exact

The diagram shows nonzero transmitted probability without solving a real barrier equation.

toy amplitude model, not material data\text{toy amplitude model, not material data}
Toy tunneling modelOnly the displayed probability budget is claimed.R=3/4T=1/41/2tail P=1/4