1.I am trying to understand two-source interference pattern. I am using this simulation for clarity.
As I understand, considering in classic-terms electromagnetic wave has both positive and negative magnitudes, i.e. its electric and magnetic components changes its values from some negative to some positive.
Due to superposition, negative and positive waves with same amplitude should cancel each other.
So, if consider em wave, as wave, that has negative values, as well as positive, we will have the next illustration:
In all interference (or diffraction) illustrations, explanations or simulations, (for example, like I mentioned above) I found, wave lines are colored same color, that is confusing me. Maybe they are considered wave as one-signed oscillation process?
However, if to consider waves as two-signed oscillation with positive and negative values, known two-source interference pattern seems to be partially wrong. How it should be:
From illustration above (if drew it correctly, maybe I missed something) we see, that, indeed, middle interference is constructive, but each second interference (every even interference) (in both direction from the middle one), should be destructive, because there occurs superposition of waves opposite magnitudes.
And on the screen, as I drew it in the right side of illustration, we should have at center higher value (sum of two waves), then in both direction, lower value (one wave) and not zero (!), then zero (sum of two opposite waves), then lower value (one wave) and all again. After wave half period - all the same, but with opposite sign.
Where do I wrong?
2.One more little question: do I understand correctly, that experiment with one source and two-split obstacle is more "popular" instead of just two monochromatic sources, because it is hard to make them coherent?
Well, I searched more images, that illustrates interference, like this, which seems to be correct, but at the same time this image illustrates each interference as constructive, as well as simulation, that mentioned at the beginning of this post.
So, it seems that they are either wrong, either consider waves as only with one sign, or has wrong scale between interference and detector pictures.