Howdy,
Thanks for looking it up. Wikipedia rocks
However, one thing it cannot do is interpreting the data it presents:
fishnutham;653259; said:
sorry harley but you're wrong light passing thru a window will create algae growth
I never said it ain't so
Light causes algae growth, that is undisputed. All I say is that it's not UV light!
fishnutham;653259; said:
just because you dont get the spectrum that causes sunburn dosnt mean windows block uv.
Sunburn is caused by UVA and UVB, with a peak at 320 nm. Since you cannot get a sunburn sitting next to the window, we can safely assume that window glass blocks UV efficiently in that range of the spectrum. In addition, light has to penetrate the aquarium glass plus the water, both of which, yet again, absorb UV. What finally ends up at the target site is negligible.
fishnutham;653259; said:
Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths while Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm
First, let's stay on track: I was not talking about specialty glass here
Let's stick to window ("ordinary") glass. That 90% statement is a very wild quote from Wikipedia. Absorbance is directly proportional to the thickness of the sample (Lamber-Beer's Law). That means it depends on what window you have in your house (double-insulated or 1960s thin as in my town-home where I currently have ice on the inside of my living room window
brrrrrrrr).
Anyhow, let it pass those 30 nm from 350-380nm in the near UV. As a generalized statement, I think it is still fair to say that windows block UV completely from 1-350nm (remember sunburn maximum at 320nm is blocked completely) and above that still
partly (350-380 nm) (I state that as a tribute to your research and Wikipedia
) - which is of no relevance here, because:
Last but not least, we are talking about the
spectrum of the light which induces algae growth. Specifically green algae. As the name says, they are photosynthetic organisms. Photosynthesis, however, is powered by wavelengths of 680 and 700 nm (photosystem II and I). Neither chlorophyll nor proteins associated to it in some other algae (phycoerythrin in red algae and phycocyanin in blue-green algae/bacteria) don't really absorb in the UV spectrum ... no absorbance, no power, no life.
[this graph shows absorbance ex vivo. It changes slightly to higher wavelengths in vivo]
Bottom Line: Let's say the root of all evil is the light that passes thu the window and reaches her tank, not the UV light, okay?
HarleyK
fishnutham;653264; said:
just on a side note what do you think causes your furniture and carpet to fade where it gets direct sunlight from the windows
It's the light of the wavelength absorbed by the respective item. Absorption of light can over time lead to decay of the respective dye. A green carpet fades because if absorbs red and blue. A blue table fades because it absorbs green and red. A red door fades because it absorbs green and blue. UV causes cracking and brittleness in exterior applications (garden hose, old house paint). However, just by absorbing UV light, items do not fade in their colors!
