Splitting the wave function of a particle in a box

This paper addresses the question of what happens to a particle in a box that is initially in the ground state, when the box is split into two slightly unequal halves. If the splitting is done sufficiently slowly, it is found that the particle always ends up in the bigger half of the box, regardless of how small the difference in sizes of the two halves may be. Approximate analytical expressions that describe the process are derived, and an optical analogy is presented. (C) 2002 American Association of Physics Teachers.