Thin Lens Equation Calculator mechanism

Model scope

The thin-lens equations and honest-label claim are appropriate, but the instrument needs an explicit sign convention, unit policy, input constraints, singularity behavior, and classification rules before it can receive PASS.

• The formulas are standard only under an explicitly stated sign convention: f>0 for converging lenses, f<0 for diverging lenses, do>0 for a real object, and di>0 for a real image.
• The formulas do not specify the classification rules that convert the sign of di and m into real/virtual and upright/inverted outputs.
• The specification does not define behavior at the focal-plane boundary do=f, where the image is at infinity and finite di and m do not exist.

Units and conventions

• f and do must use the same length unit before substitution; di is returned in that same unit.
• This review assumes the real-is-positive convention: converging f>0, diverging f<0, real object do>0, real image di>0.
• Under this convention, di>0 means real and di<0 means virtual; m<0 means inverted and m>0 means upright.
• The thin-lens and paraxial approximations apply, so object and image distances are measured from the lens's principal plane.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "f": 50,
    "do": 300,
    "unit": "mm"
  },
  "expected_outputs": {
    "di": 60,
    "m": -0.2,
    "image_type": "real",
    "orientation": "inverted"
  },
  "working": "1/di = 1/f - 1/do = 1/50 - 1/300 = 6/300 - 1/300 = 5/300 = 1/60. Therefore di = 60 mm. m = -di/do = -60/300 = -0.2. Since di>0, the image is real. Since m<0, it is inverted."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The singular inputs do = f and do = 0 require explicit rejection or infinity handling, and the signed-distance convention is unspecified. Without validation and a documented sign convention, the calculator can produce undefined results or a different image type and magnification for the same physical setup.

Other records

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
• BOUNDARY_HAZARD_CATALOG.json