The interference pattern on the left                The pattern on the right formed after
                             formed after pulses from a cathode ray         the bursts/pings from the cathode ray
                             gun were fired through a single slit.                 gun were fired through two slits.

                                                       Double Slit Experiment Conclusion

A picture reproduction of the final target panels (for both single slit and double slit), that were originally photographed at progressive stages by Dr. Tonomura, resulting from cathode ray pulses or pings allowed to accumulate, is immediately below this written section.

Medium charged photons—those close to an middle charge between strong positives and those with no charge—that flow from cathode ray guns are repelled from both radio and electron shell particles when they pass by those in close range. Meanwhile, passing through the slits a bit more distance, they are slightly attracted to the atoms that make up the panel because there is always a tiny amount of leftover attraction from every atom: such as enough to add ½ of a radio particle or ½ of a regular electron, also some attraction due to a few photons being knocked off nuclei almost constantly that always need to be replaced. This is the reason for the interference pattern on the target screen. Particles emitted by a cathode ray gun are either pushed away from (are lightly deflected from) radio or electron shells as they pass by close to them... or they are pulled to one side or to the other by a very mild attraction to the overall collection of atoms in the panel with the slits. This yields the pattern on the target screen with no need for any alleged wave cancellation on the downstream side of the slit panel. (Keep in mind that cathode ray particles may lack enough repel to avoid a head-on collisions with radio particles or beta electrons. But that's more of a side note, not all that important to understanding this; as there is much more to explore on that.)

Now on whether the act of “observing” the particles just before they pass through the slits changes the interference pattern as quantum mechanics alleges: Anyone who is familiar with how CRT monitors work will realize that cathode ray gun particles are deflected by an electrically powered magnetic field placed at the end of such a gun moment by moment, to strike the interior of a glass face, one in which the inside has been coated with a phosphor, which phosphor excites to generate a color that pro-ceeds forward on through the transparent glass. However, there is no need to go into any of those various specifics right here.

The point is that when a magnetic field is sufficiently concentrated it will deflect cathode ray particles. And even if a magnetic field wasn't that concentrated, it most likely still deflects them a small amount. The reason this doesn't happen on the sides   of magnets with light is that the amount of light scattering is overwhelming compared to the very low concentration of the magnetic field. Also, many of the photons in typical visible light are a bit lower charged than cathode ray photons, which makes them more ambivalent. Notwithstanding, since the instrumentation used to “observe” which slit a cathode ray pulse passes through generates a field to do so (unlike say your eye, which observes without such a field), that field will no doubt DEFLECT the particles so they will generally pass through one slit, which is why the interference pattern matches what appears when a panel with just one slit is used. Therefore, actual observing—i.e. simple observing or simply observing—doesn't change any of that as how we have been told it does.

Bear in mind that focusing is achieved in mass spectrometers, though whole atoms within projected vapors aren't likely deflected much, if any, at that emission point. Still, a few atoms are perhaps deflected, but those simply veer off to the sides and don't reach the target.

Focusing a cathode ray beam has also been achieved. But once again, a few particles lost to the sides aren't noticed since the beam propagating straight ahead is concentrated; while any individual particles lost to the sides are so few in comparison. However, if cathode ray beams consist of medium charged photons, by those being individuals of very low mass they are deflected far more than any atom would be, especially since they have innate repel not just to one another but to the surfaces of all that comprises atoms.

There is also a stark difference between sound waves and light waves. Sound waves create crests and valleys of vibration through atoms—typically gas atoms and molecules that are in virtual constant contact with one another—which waves propagating through water serves as the perfect analog. Those can of course be canceled if the timing is such that a peak from one direction is met with a valley propagating from a different direction; or perhaps in opposing waves peak against peak is what it takes to cancel one. Light, on the other hand, is actually particles (typically waves of them moving out in all directions) that fly right past and/or through gas atoms and water molecules without compressing them as sound does. For sound does not have a physical medium since sound occurs by the compression of substances already present; even as without the presence of touching physical mediums—as in space—there is no sound.

      This reproduction's dots (just below) are evenly spread, whereas the strikes on the target screen exhibit randomness.