
$$
   | p_x | \sim  \Delta p_x  \sim  {{h}\over{2 \pi L }}
$$

\medskip

$$
   {\rm fractional\ uncertainty\ } = { {\Delta E } \over {E} }
$$

\medskip
$$
   \Delta t \simeq 10^{-8} {\rm \  seconds}
$$

\bye
