The answer may be in your "Mac Help"
From the Apple site…
Opening your iBook's optical drive tray and ejecting a CD or DVD
Learn how to Eject a CD or DVD or Open the Optical Drive Tray of an iBook with a tray-load optical drive. For iBook models with slot-load drives, see Mac Help for your model of iBook.
Make sure the disc is not in use.
Quit all applications that are using files on the disc.
Press the Media Eject key at the top-right corner of the keyboard.
If that doesn't work, hold down the function key and press the Media Eject key.
If that doesn't work, drag the disc's icon to the Trash.
If that doesn't work, restart the computer, and hold down the mouse button as the computer starts up.
To restart, choose Restart from the Apple menu.
If the disc still won't eject, eject it manually
Carefully insert the end of a straightened paper clip into the emergency eject hole on the drive tray.