In case when we don't observe the presence of an electron at either slit, there is an interference pattern, in case we do observe there is a 2 band patter, as an electron would be a particle. I understand that without an observation, the state of an electron in a superposition of all eigen values of the wave function, and the fact of "observing" means measuring device by interacting with the electron changed its wavefunction in a way that it is now has a defined solution. I agree that, when we observe an electron at both slits, for any case when electron goes through either slit it will have a defined state and it will behave as a particle, thus we have 2 lines on the screen, corresponding to each slit. But: 1. What if we observe an electron only at 1 slit, will the result on the screen be one vertical line from the observable slit, and wave distribution from non-observable slit? 2. When electron is observed it is localized, but when it travels further will it again get a wave behavior as the distance from the observable position increase? Meaning if we observe the electron not at the slits but at the source of the electron, and then while it will reach the slits it will behave as a wave again. 3. In case we have 3 slits and observe only at 1 slit, will the resulting pattern be 1 vertical line, and interference pattern caused by non observable 2 slits? Thank you.