  In this letter, the wavelet transform is used to decompose the classical
linearly polarized plane light wave into a series of discrete Morlet wavelets.
It is found that the energy of the light wave can be discrete, associated with
its discrete wavelet structure.It is also found that the changeable energy of a
basic plane light wave packet or wave train of wave vector
$\mathord{\buildrel{\lower3pt\hbox{$\scriptscriptstyle\rightharpoonup$}}\over
k} $ and with discrete wavelet structure can be with the form of ${H_{0k}} =
n{p_{0k}}\omega$ $(n = 1,2,3,...)$, where $n$ is the parameter of discrete
wavelet structure, $\omega $ is the idler frequency of the light wave packet or
wave train, and ${p_{0k}}$ is a constant to be determined.This is consistent
with the energy division of $P$ portions in Planck radiation theory, where $P$
is an integer. Finally, the random light wave packets with $n=1$ are used to
simulate the Mach-Zehnder interference of single photons, showing the
wave-particle duality of light.
