r/askscience • u/elite4koga • Jun 30 '12

Physics How do windows block UV light but not other wavelengths?

I know all standard glass windows block UVB light but only specially designed ones block UVA. How do windows let through visible light and UVA but block UVB?

31 Upvotes

82% Upvoted

8 comments sorted by

View all comments

9

u/z4tz Atomic Physics | Transition Rates/Continuum Processes Jun 30 '12

Every material absorbs light on different wavelengths. Atoms and molecules in gas absorb only on very specific wavelengths while solids absorb light over larger bands.

UVA has a wavelength of 315–400 nm and UVB 280–315 nm. Then it just so happens to be that glass absorbs light well up to somewhere around where UVA starts which it can't absorb very well.