Suppose I have a particle confined between 0 and d on the x axis, and it has some wavefunction, if I measured the particle to be between some small interval [a, b], would the wavefunction collapse into a rectangle-like function with equal prob. density on the interval and zero outside? or what? Suppose, instead, that I measured the region [a, b] and did NOT find the particle there, it is reasonable that the wavefunction would be affected (i.e. it must become zero on [a, b]). Right or wrong? and if right how will it look like?