The flash of a light stuns a hamster based on the type of light it is, a black light does not stun a hamster neither does a flash light, but, a stobe light will stun a hamster and could cause sesiures or other brain related issues. Also you have to becareful with spot lights as they may cause blindness.
I believe that this would confuse a hamster or possibly limit their vision for a second, but cause no direct harmful effects besides a momentary disorientation.
Flashing lights at a hamster won't cause any real physical harm but it can cause emotional/mental harm. Essentially the hamster is being constantly terrorized, this should stop.
I don't think it will stun him, but it can't be good because a hamster is a rodent and they are usually nocturnal and don't like light that much. Also, it might scare him and cause him to startle and hurt himself. Also, it might hurt the hamster's eyes.
Yes, this is really bad for hamsters! Take photos without flash, cause flash can really damage their long-term eyesight. Once in a while is ok I guess, but please try to avoid using flash on nocturnal animals!