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Sandbox Physics

Optics 044 · Interference, coherence, cavities, and metrology

Interference Surface Metrology

An independently initialized three-dimensional apparatus connects Newton rings, Air wedge, Fizeau optical-flat test. Two dimensional physical controls, direct probe dragging, a detector trace, and three quantitative checks are recalculated from the stated equation.

Interactive modelInterference Surface Metrology
Primary prediction P1\mathcal P_10.500.50
Physical scale P2\mathcal P_250%50\%
Limit check V\mathcal V0.00π0.00\pi
Model regimevalid model regime\text{valid model regime}

Physics tutorial

How to investigate Interference Surface Metrology

BackgroundInterference Surface Metrology is one independently initialized apparatus with three linked investigations: Newton rings, Air wedge, Fizeau optical-flat test. Its two controls—Surface radius and Wedge angle—feed the governing relation 2nt=mλ2nt=m\lambda. The validity indicator marks the paraxial, lossless, weak-field, or steady-state assumption used by this apparatus.

Why it mattersHow can fringe geometry reveal thickness, curvature, and tiny surface defects?

Start with the essentials

Focus question
How can fringe geometry reveal thickness, curvature, and tiny surface defects?
One-sentence intuition
The detector curve and all three numerical readouts are recomputed from 2nt=mλ2nt=m\lambda. Geometry and glow are presentation encodings; the equation, units, conservation or limit check, and validity indicator are the quantitative evidence.

Core mathematical model

Governing relation

2nt=mλ2nt=m\lambda

The implementation evaluates this relation with dimensional inputs and an executable analytic or numerical benchmark. The validity indicator marks the paraxial, lossless, weak-field, or steady-state assumption used by this apparatus.

Common difficulties

Mistaking glow for measured power

Typical misconceptionA brighter cinematic trail must represent proportionally more optical power.

Better mental modelUse the detector and normalized readouts for comparison. Glow is deliberately nonlinear so weak structure stays visible.

Run the experiment

  1. 01

    Scene 1: Newton rings

    Select Newton rings. Sweep Surface radius, hold Wedge angle fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.
  2. 02

    Scene 2: Air wedge

    Select Air wedge. Sweep Surface radius, hold Wedge angle fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.
  3. 03

    Scene 3: Fizeau optical-flat test

    Select Fizeau optical-flat test. Sweep Surface radius, hold Wedge angle fixed, and then reverse the roles. Drag the stage probe to repeat the first sweep directly.

    What to observe: Read the primary prediction, physical scale, limit check, and validity indicator together. Record where the approximation boundary changes.