How to find this out on Your Iphone 5?

At school my teacher left his IPhone 5 on his desk so one of my friends picked it up and selected the photo app he didn't select any of the pictures or anything he just quickly looked and went out of it. But when the teacher came back to the class and checked his phone he said who has been looking at my photos on my phone? But how did he know?

When you hold down the home button recent apps appear

Maybe he left the app open

You don't hold down the home button.

If you unlock the phone then double tap the home button it opens up all the apps that are still running. It's like a task manager on your computer.

Even when you come out of the app it is still running in the background (using up battery power) so you double tap home and then close it in there. He probably seen it through there.

Prime example of why you should put a pass-code on your phone.

The Multitasking Thing? Or maybe he saw the student leave his desk i don't know.