(February 12, 2016 at 3:04 pm)Excited Penguin Wrote:(February 12, 2016 at 11:12 am)Cthulhu Dreaming Wrote: Penguin - the idea here is that you have two signals (lasers) which, due to alignment, are 180 degrees out of phase with one another. When you combine the two signals, they cancel each other out. If you slightly modify the distance the beams have to travel, the signals are no longer out of phase and therefore not completely canceling out, making the perturbation apparent.
ETA: I see that Alex and TRJF have provided explanations already. Another doesn't hurt.
Yes. What I don't understand is how the beams cancel each other out and how the distance they have to travel has any bearing on whether they cancel each other out or not at that ridiculous angle they meet at to begin with. But I think that just has to do with my lack of understanding of how light waves behave, and so on.
Think of it this way: in a pond, you drop two rocks, exactly the same weight, at exactly the same time. They each set up a ripple of their own waves, and at a certain point, those waves are identically strong, but headed in the opposite direction.
If the waves contact each other exactly half the distance between the rock-drops, they will be exactly as strong, and counter each other out. Any discrepancy beyond that may be adduced to the influence of another body.
