I recently read a book by Richard Feynman that had the passage quoted in the link below, stating that bright light can never hurt your eyes and its ultraviolet that does the damage:
https://www.realclearscience.com/blog/2016/04/what_its_like_to_actually_see_an_atomic_explosion.html
I’m not sure what this means, only wavelengths outside the visible range can hurt your eyes, and visible range radiation is safe no matter how bright and powerful it is?
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Yeah, I always thought he was wrong about that.
Even visible light can cause heating of the retina, leading to damage. Just look at a visible LASER for an example.
A sufficiently bright light would vaporize your eyeballs and make them explode along with the rest of your body. So he is obviously wrong, there has to be some level where it will start to cause damage. And as mentioned above,powerful visible-light lasers are known to cause permanent blind spots on the retina.
Just staring at the sun during an eclipse can cause permanent damage.
Any welder knows not to look at the bright light.
That’s why they wear a welding helmet.
I hesitate to doubt him, but it sounds like he was just wrong.
But welding produces copious ultraviolet radiation, so that doesn’t refute Feynman’s statement.
Looking at the quote from Feynman, it sounds like a loose offhand comment that wasn’t really meant to be taken literally, but more like a poorly worded way of saying “UV radiation is likely to be more harmful – and in this case perhaps emitted more intensely – than visible light”, which indeed it is, because of the higher photon energies. But it’s self-evidently obvious that visible light is just EM radiation that, if intense enough (as in the case of visible-light lasers) can cause permanent damage (such as vaporizing the target!).
If there’s a grain of truth in that statement, it’s that the human eye will close (blink) reflexively when exposed to bright visible light. It doesn’t do that for UV or IR. So in that sense, a bright visible light is safer.
But obviously, a sufficiently bright visible light will damage your retina before the eye can close. For lasers, that is the dividing line between class II and class III. Class III and above are dangerous because they are too bright for the blink reflex to protect your eyes.