Anyone that's been in a museum knows that's it's forbidden to photograph mainly old or very deteriorated crafts using a flash, but what is the reason for this? I don't see how a burst of relatively low intensity, non-ionizing radiation can have a long-term harmful effect on every kind of material. Or is it that some flashes radiate ionizing frequencies/intensities? Last equinox, at the (if I'm not mistaken) Kukulcan pyramid in Mexico, there was a festival in which they projected a series of lights at it as can be seen in this Facebook video and this sparked a discussion between me and my friends because one of them thought they were lasers and they were harmful to the structure according to one of his recent classes.
I think it's appropriate to break down the question into the following:
What is the actual effect flash lights from cameras have on materials?
If there is such, how is it generated and how does it differ from other light sources?
Could an adequate-power-laser-show really harm a structure like an old pyramid? Are there any differences between the kind of erosion or decay caused by lasers and flashes?
Please try to interpret the question in the broader sense, with the laser and pyramid example, not just the use of flash in a museum.