I remeber reading once about a boy either in Nagasaki or Hiroshima at the time the nuclear bomb went off.
He said that he covered his face with his hands, and still the light was as bright as though he were looking at the sun.
This has me wondering, can light be so bright, that it will go through materials it normally would not go through? For example given enough intensity, will a powerful source of light inside a room radiate outside?
Yes, but light is just radiated energy and creating a beam of light bright enough to penetrate a brick wall would incidentally be more than powerful enough to destroy the wall.
Human flesh, on the other hand, is comparatively translucent - you can shine the light of a powerful halogen spotlight thtough the flesh of your hand - it isn’t hard to imagine that a light many times more intense (but still not powerful enough to instantly vaporise your hands) would be able to shine through both your hands and your eyelids.
Go in a totally dark room and hold a flashlight up to the palm of your hand and look at the back of your hand. Now imagine that light is magnified a squillion times.
Light is like any other electromagnetic source. Different materials impede it to differing degrees. If it’s strong enough, enough light will permeate to be visible to the naked eye. It’s not a does-or-doesn’t-block proposition.
I can’t comment specifically on the nuclear bomb anecdote (not sure how he lived to tell the tale).
Furthermore, the boy would not have been seeing only visible light. Radiation passing theough his eye and brain would have unleashed cascades of photons in his eye (Cerenkov effect), directly and indirectly stimulated the neurons in his retinal/visual cortex, and other effects.