Whenever you relocate or rename a file, you should _redirect_ the
old URL to the new one.
The rationale is that google will continue to refer people
to the old URL for at least a week (possibly longer), and
people may keep bookmarks for the old URL more-or-less forever,
so redirecting them is the best way to make the right things
happen.
There are ways of doing this within HTML (using pragmas) but
the preferable way is to do it lower in the protocol stack,
i.e. at the HTTP layer.
On an Apache server, you can easily do this by adding a line
to the .htaccess file in the directory where the old file
would have resided.
Here are three examples from my web site, i.e. three lines from
the .htaccess file in the http://www.av8n.com/physics/ directory.