The basic concept of the collapsing of the wavefunction can be understood be the following Double slit experiment. However my answer does not cover your aspect for a macroscopic question. First focus on basic concepts and than expand your knowledge to the not-so-easy to grasp macroscopic effects. Then consider the beautiful effects described by the John Rennie answer.
Consider reading Double slit experiment which results in a visible pattern. Incident photons/particles have to be considered as a plane wave $\Psi(z,t)$ in z direction. Propability distribution $|\Psi(x,y)|$ of the wave-funkction is proportional to intensity on observation screen.
This experiment performed by Young astonishly can be performed with electrons and even larger particles like neutrons. The conclusion is particles that have to be modelled as waves (under certain conditions). The solid picture of particles still helps in other models.
Interference with oneself
This is easly more confusing. For a start neglect this fact. For advanced understanding of this concept, try to depict the equal experimental result, if one particle at-a-time is used in this experiment. (Somebody can edit an example of this in my answer)