Abstract

An atom is confined to a box in its ground state. An attempt is made to observe it in the left half of the box by scattering photons out of a photon wave packet passing through this half of the box. If no photons are scattered, the atom is missing. It is located on the right side of the box and its wave function is changed. The expectation value of the combined atom and photon energy is increased. For the other alternative, that the atom is found on the left side, the expectation value is decreased. By including both alternatives, it is shown that the mean energy is conserved