Thin Film Interference

Dave Nero


This simulation shows the results of thin film interference. The wavelengths that are brightest (fully constructive) and darkest (fully destructive) are calculated. Use the sliders to adjust the index of refraction for each of the three layers, along with the thickness of the thin film. You can use the drop down menu to switch between reflection and transmission. The check boxes are used to highlight the path length difference and to show the location of 180 degree phase shifts. The horizontal component of the light rays are exaggerated for clarity. The calculations here assume that the light is perpendicular to the surface.
  1. What factors determine the wavelengths for the maxima and minima?
  2. Visible light ranges from roughly 400 nm (blue) to 700 nm (red). Light outside of that range is not visible. What settings produce the most maxima within the visible spectrum?
  3. Can you adjust the sliders to create a thin film that would appear green, and only green (about 500 nm) when viewed in reflected light?
  4. Why won't visible light reflect off of an especially thin film?