quantum mechanics - What happens when we manipulate the observer in the double slit experiment?

Consider the following alterations to the double slit experiment:

• turn the observer on and off rapidly


• move the observer further and further away, until the point at which it can no longer effectively observe

What happens to the wave function when the observer turns off and then back on rapidly, to the electron in flight? When moving the observer further away, at what point does the wave function no longer treat it as an observer?