How do i confirm data is "backed up" on external Hard Drive?

I'm a PC user so i hope i'm doing this right....Christmas present for my wife's MacBook Pro, I purchased a Seagate 1Tb external hard drive. Pretty simple. Connected it, and Time Machine takes over and backs up automatically via the USB connection.

Except that when i click on time machine, i'm not really convinced that the external HD has everything backed up that it should. Specifically, when i open Time Machine, i am unable to view photos on iPhoto. This is my wife's greatest concern. Please help, and thank you.