B Can sunglasses fully protect against UV sensitivity?

[DaveC426913]

TL;DR Summary

I know quality sunglasses *block* UVA and UVB, but what wavelength are they *sensitive* to?

Is there a 1:1 correlation between the wavelengths that a given pair of quality sunglasses blocks and the wavelength that trigger the photochemical change?

For example: if I know my wife I am particularly sensitive to UVB light, and my wife's my sunglasses only darken under UVA light, then I could be getting exposed to UVB light unwittingly.

(Although I guess that would make for a pretty darned useless - and a falsely advertized - product. Which means I guess I answered my own question.)While I'm on the subject: can UV light pass through a car (side) window? If (someone I know) is regularly developing a rash (in the space of ten minutes) from light falling on her skin through a car window, is that likely UV exposure, or is it possible that skin can be sensitive to visible light wavelengths? (Maybe I should move this last question to Medical & Biology.)

 

[hutchphd]

@DaveC426913 Good graphs at the end. https://www.gmp.ch/spectroscopy-app...racteristics-of-sunglasses-and-tinted-windows

 

[DaveC426913]

@DaveC426913 Good graphs at the end. https://www.gmp.ch/spectroscopy-app...racteristics-of-sunglasses-and-tinted-windows

This seems to indicate that UVA (315-400nm and the least harmful) is the only one that has any significant transmission.

(my annotations in red)

 

[Orthoceras]

quality sunglasses ... what wavelength are they *sensitive* to?
... the wavelength that trigger the photochemical change?
my sunglasses only darken under UVA light, ...

"Photochemical change" and "darkening under UVA light" is typical for photochromic sunglasses. Are you perhaps using the word "quality" as a synonym for "photochromic"?

 

[DaveC426913]

Are you perhaps using the word "quality" as a synonym for "photochromic"?

Sure. I simply mean to head off digression into the consequences of sunglasses that are simply tinted or whatever.

 

[Orthoceras]

Many sunglasses have polycarbonate lenses. Polycarbonate inherently blocks UVA and UVB (cutoff at 400 nm). The unrelated phenomenon of photochromism occurs in a specific lens coating. It can be induced by visible violet and by ultraviolet.

(Fun experiment: a photochromic polycarbonate lens does not darken when held backwards in sunlight)

 

[Rive]

TL;DR Summary: I know quality sunglasses *block* UVA and UVB, but what wavelength are they *sensitive* to?

Is there a 1:1 correlation between the wavelengths that a given pair of quality sunglasses blocks and the wavelength that trigger the photochemical change?

Just a remark. It's nice to have the excess intensity of visible light reduced, but with the stray UV factored in it's also potentially harmful since the pupils gets unnaturally extended, wide open for any UV bypassing around the edges of the sunglasses.

I don't think it would be anything dangerous for a simple photocromatic lens, but it tells a story that - for example - those fancy round sunglasses are NOT recommended for climbing, sailing or for any UV-intensive environment.

When it matters the edge of device sticks to the skin and does not let any stray UV in.

(random 'climbing sunglass' from the internet)

 

[berkeman]

(Fun experiment: a photochromic polycarbonate lens does not darken when held backwards in sunlight)

I will try that!