Why is it dangerous to look directly at the sun wtith sunglasses?
Because the light of the sun is so bright (and that includes
components outside the visible range, such as ultraviolet light) that it can
very quickly cause permanent eye damage (via destruction of the light-sensitive
cells in the retina, initially); ordinary sunglasses simply don’t provide enough
attenuation of the light passing through them to make the sun dim enough to
safely view in this manner.
Direct
viewing of the sun should not be attempted without using a filter specificallyapproved for this purpose. Welding filters of shades 12–14 are an example - and
these are so dark that they’ll appear practically opaque if you look through
them at a normally-lit scene!

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