  The interaction of a wave packet (and in particular the wave front) with a
mass barrier is investigated in one dimension. We discuss the main features of
the wave packet that are inherent to two-dimensional wave packets, such as
compression during reflection, penetration in the case when the energy is lower
than the height of the barrier, waving tails, precursors, and the retardation
of the reflected and penetrated wave packets. These features depend on the
wave-packet envelope function which we demonstrate by considering the case of a
rectangular wave packet with sharp front and trailing edges and a smooth
Gaussian wave packet. The method of Fourier integral for obtaining the
nonstationary solutions is used.
