Make wave detector probes snap to ray

[arouinfar]

During interviews, I observed a few students switch between the wave and ray modes while using the wave detector on the More Tools screen. When switching from the wave to the ray mode, it is easy to lose the signal because the probes are no longer precisely centered over the ray. Students may attribute this lack of signal to some inherent property of the ray, because it is not always obvious that the probes need to be moved.

For example, the probes are initially placed on the wave

After switching to ray mode, the crosshairs of the probes are not exactly centered over the beam, and the signal is lost. However, it's not immediately obvious to students that the probes need to be moved. Instead, they connect the lack of signal to something about the ray itself.

To avoid situations like the one described above, I think it would be nice to have the probes "snap" to the nearest point of the ray when switching from wave mode. The snapping would only occur if the probes were reading a signal while on the wave immediately before switching to the ray mode.

I realize that moving the probes will result in some discontinuity in the phase, but I think that is acceptable. The change would happen very quickly at normal playback speed and would be unlikely to be noticed.

This is not a blocking issue that needs immediate attention, but it would nice if @samreid could address it in the next version of the sim (whenever that may be).

[samreid]

A related feature would be to have the probes stay "snapped to" the light when its angle changes. Currently it is difficult to investigate wavelength changes when changing the index of refraction because the angle of the light changes and it leaves the probe behind.

[arouinfar]

That's a great suggestion @samreid!