This is a simple simulation of thin film interference. The red curve is the incoming wave,
the blue the reflection from the first surface, and the green the reflection from the second.
What is not simulated is the changes in levels. This to make it easier to see the relative phases.
The gray curve in the separate window show you the reflected wave, i.e. the sum of the blue and
the green curves.
You can select three different selections of refractive indices. You can move the right surface with the keys Q, W, E and R. Q and W moves the surface to the left, Q faster and W slower, and E and R move the surface to the right, E slower and R faster. You might have to click somewhere in the figure to make this work.
You may also hold down the mouse button as the mouse pointer is to the right or left of the surface. The further away the faster. You may also touch the screen to the right or left of the surface. You can halt and restart the simulation with the Esc key. Touch to the left of the blue line will do the same.