Source: https://guthlabs.ai/docs/instruments/snell-s-law-refraction-calculator/implementation/

instrument implementation / implementation-contract

# Snell's Law Refraction Calculator implementation

A source-bound implementation contract for Snell's Law Refraction Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-132

**Effect**: Computation or source lookup only

## Input and validation requirements

- If n2 is zero, the inverse formula divides by zero.

- If n1 or n2 is negative, the physical interpretation requires handling complex or signed refractive indices; this is not specified.

- For light going from a higher-index medium to a lower-index medium, an input above the critical angle produces an inverse-sine argument greater than 1 and must be reported as total internal reflection rather than NaN or a fabricated angle.

- Passing degree values directly to JavaScript Math.sin or Math.asin, which use radians, causes incorrect results; explicit conversion is required.

- The interface-normal convention is not stated, so complementary angle results are possible if users measure from the surface.

- A refractive-index table requires wavelength, temperature, pressure, and material-state assumptions; a generic air/water/glass/diamond table can be misleading without those qualifiers.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "mode": "solve_theta2",
    "n1": 1,
    "n2": 1.5,
    "theta1_deg": 0
  },
  "expected_outputs": {
    "theta2_deg": 0
  },
  "working": "sin(theta2) = (n1/n2) sin(theta1) = (1.0/1.5) sin(0 degrees) = (2/3)(0) = 0. Therefore theta2 = asin(0) = 0 degrees."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/snell-s-law-refraction-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/snell-s-law-refraction-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/snell-s-law-refraction-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`