In a double slit experiment (say, of electrons), when putting a detector to examine the passing of electrons through one slit, the wave pattern of the electrons disappears and instead the particle pattern appears. The classical explanation is that an electron exists both as a wave and as a particle the same time, but the wave feature of an electron disappears when it is observed. Several questions come to me for such an explanation. 1) The so called "wave pattern disappears when particles are observed" is not exactly true, because we observed the wave pattern anyway, be it observed by a film or something similar. 2) Let's assume the wave pattern was observed by a film in the back of the two slits. If we use multiple layers of semi-transparent films, will we be able to see the wave pattern on the first layer and other layers? If yes, the belief that observing an particle destroys superposition (of multiple possibilities) or wave feature does not hold. 3) If we use 3 slits instead of 2 slits, and we use an electron detector to observe one slit, what will happen? Has anyone actually done such an experiment? I've seen people reasoning and debating what could happen but have not seen any experimental results. It is a big surprise that such an experiment has not actually been carried out. Such an experiment would be very interesting. Thanks for any discussion or information.