  Extra-dimensions are a common topic in popular descriptions of theoretical
physics with which undergraduate student most often have no contact in physics
courses. This paper shows how students could be introduced to this topic by
presenting an approach to two basic consequences of the presence of compact
extra-dimensions based on undergraduate-level physics. The insensibility of
low-energy physics to compact extra dimensions is illustrated in the context of
non-relativistic quantum mechanics and the prediction of Kaluza-Klein
excitations of particles is discussed in the framework of relativistic
wave-equations. An exercise that could be used as a follow-up to the "particle
in a box" is proposed.
