How does the black sharpie challenge work?

Sharpie shock challenge – see how to make your phone “shock” you by using a sharpie and the flash of your phone camera.
How it works?
1. Students draw a black square on their arm with a Sharpie.
2. They open up the camera on their phone and turn on the flash.
3. Then put the flash of the phone where the Sharpie square is drawn.
4. Take a picture.
5. The result is a “shock” to your arm.

This occurs because apparently caused by the black marker absorbing sudden heat from the phone flash.

Be sure to Put the flash on your phone directly on the black sharpie square.