Is one particle detected on the detection screen for each particle shot in a double slit experiment? Or do some particles fail to be detected because they hit the barrier in between the two slits? In other words, is there an exact one to one correspondence of particles shot to particles detected? I was corrected by someone when I maintained that, in a double slit experiment, one never finds a particle in both places, or neither places, when you look. I think he is right, it could fail to be detected, but it hasn't been clear to me when reading the actual experiments.