mma-interference

Manipulate[With[{l = l2},
  p1 = Plot[Sin[4 x], {x, 0, l}];
  p2 = Plot[Sin[4 x], {x, l, 2 l}, PlotStyle -> Red];
  Graphics[{Black, Thick,
    Tooltip[Line[{{0, -1}, {0, 1}}], "Dielectric entrance"],
    Tooltip[Line[{{l, -1}, {l, 1}}], "Dielectric exit"],
    Tooltip[p1[[1]], "Transmitted wave"],
    Tooltip[GeometricTransformation[p2[[1]],
      ReflectionTransform[{1, 0}, {l, 0}]], "Reflected wave"]},
   PlotLabel -> "Interference Filter"]], {{l2, Pi/2,
   "Dielectric thickness"}, Pi/2, 2 Pi, Appearance -> "Labeled"}]