Too bad: it is indeed possible to restart a Raspberry Pi 2 by using a high power flash.
It appears that U16, the SMPS chip, is the culprit.
Yes, bit of bluetac on that chip and it survives the flash
Source: Raspberry Pi • View topic – Why is the PI2 camera-shy ?
Simon Stuart checked it:
it’s true!
Put the high-power flash (which I believe uses a Xenon bulb) on my camera, and behold a shot to the top of the board does indeed crash it every time!
Never in a million years would I have thought such a thing were possible!
At first Simon could not reproduce it: you really need a high power flash.
I’m glad I didn’t order any Raspberry Pi 2 yet.
–jeroen
via: +Simon Stuart can you make your Raspberry Pi 2 devices crash by flash light?….