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Thin-Film Interference

This interactive simulator explores Thin-Film Interference in Optics & Light. Wedge fringes: n, d, θ; cos²(δ/2) colors and I(λ) at mid thickness. Use the controls to change the scenario; watch the visualization and any graphs or readouts to connect the model with lectures, labs, and homework.

Who it's for: Best once you already know the basic definitions and want to build intuition. Typical context: Optics & Light.

Key terms

  • thin
  • film
  • interference
  • thin film interference
  • optics
  • light

Live graphs

How it works

Light reflected from the top and bottom surfaces of a transparent film can interfere. The optical path difference is approximately 2 n d cos θ_f inside the film (θ_f from Snell’s law). A wedge-shaped film produces rainbow-like fringes as d changes; turning the incidence angle or adding an extra π from reflection boundary conditions shifts the fringe pattern.

Key equations

n sin θ_f = sin θ (air → film)
δ = 4π n d cos θ_f / λ + δ_extra · I ∝ cos²(δ/2)

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