Example 13 Convert $(573)_{8}$ to a binary number.
Using the formula in (2.2), we have
$$\begin{array}{l}
(5)_{8}=(101)_{2} \\
(7)_{8}=(111)_{2} \\
(3)_{8}=(011)_{2}
\end{array}$$

Thus, we get
$$(573)_{8}=(101111011)_{2}$$