99.9% of all UVB rays are filtered by glass. This is why UVB bulbs are a requirement - or lots of time outside in unfiltered sunlight.
Im not sure...plants are a big mystery to me. I do know that some plants, most common houseplants do well with just visable light - UVB is not as important. For example, my Pothos thrived for ages with just a regular fluorescent light - no UVB at all. Some plants with high light requirements do need special bulbs in order to really thrive
It is almost 100% - its the reason why we dont have to wear sunblock inside I havent had to find "evidence" for this in years, its always just been something that all the experts have told me - but i tried to look around for some for you.... its hard to find such specific info! I did find a website (http://www.critterjungle.com/content/view/42/57/) that says: "Does glass filter UVB light? Glass filters out 95% of all UVB rays. Aluminum screen filters out about 30%. If a screen cover is used between the light source and the animal, be sure the screen has 1/8 inch or larger holes. Also, make sure your light source is within 12 inches of your animals" I also looked up in "Lizard Care from A to Z" which is a book i've had for awhile that is a pretty decent book for basic coverage of general reptile care. In the heating/lighting section it says (when talking about taking lizards outside for some natural sunlight): "Only cages constructed of wood and wire should should be placed out in the sun and even they should be watched closely until the temperatures attained within are truly determined. A glass terrarium not only filters out the UV, but a glass terrarium, even with a screen top, or none, will intensify and accumulate heat." I will keep looking and try to find more "hard" evidence
I have checked with a solar meter and it DOES block most of the UVB out This is from the Wikipedia site. UVB is in the range just slightly above the 300nm but blocks most of it. Link to article. Wikipedia Plants require UVA which is above the 350nm quoted above. Hence they survive on windowsills.
Must admit my "friend" Mr. Google helped me here, but I was aware of it anyway. It should also be noted that "mesh" screens either nylon or aluminium has the same effect, as I understand it, it's the small mesh that disruptes the wavelength patterns. Just in passing, the is a new hand held light out that is UVC, this is germicidal and is now being used in hospitals etc as it kills bacteria and things like bed mites. I am seriously thinking of getting one to sterilize my viv's etc. Assuming it lives up to the claims. Link to info on sterilizing wand
