[bash] Variable interpolation in the shell

I have a variable called filepath=/tmp/name.

To access the variable, I know that I can do this: $filepath

In my shell script I attempted to do something like this (the backticks are intended)

`tail -1 $filepath_newstap.sh`

This line fails, duuh!, because the variable is not called $filepath_newstap.sh

How do I append _newstap.sh to the variable name?

Please note that backticks are intended for the expression evaluation.

In Bash:

tail -1 ${filepath}_newstap.sh

Use curly braces around the variable name:

`tail -1 ${filepath}_newstap.sh`