More To Tortoise Lighting Than "Meets The Eye"

MichaelaW

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@Markw84 . Need your help regarding UVA please.
I was under the impression that there is a certain amount of the UVA spectrum carried with all light bulbs.
UVA is at 400nm bordering where the visual light spectrum starts.
When I got my LED lights for my tort house I got the red and blue spectrum. I can't find the exact LEDs I got but I'm sure they were blue at 415 nm and red at 660 nm. Because it looked like a disco from the 70's I later added some white LED's to mask the visual red and blue look. The aim of all this was to get plants to grow. Plants need UVA, correct?
Does UVA pass through glass, as it sits at the low end of the visual spectrum.
If not how do we manage to grow plants indoors without UVA. For example I've grown chillies/tomatoes in my house on the windowsill. Then there's green houses, Polly tunnel etc, how does UVA get in there if it's not with light to make plants grow healthy?
Help
UVA does penetrate glass.
 

Markw84

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@Markw84 . Need your help regarding UVA please.
I was under the impression that there is a certain amount of the UVA spectrum carried with all light bulbs.
UVA is at 400nm bordering where the visual light spectrum starts.
When I got my LED lights for my tort house I got the red and blue spectrum. I can't find the exact LEDs I got but I'm sure they were blue at 415 nm and red at 660 nm. Because it looked like a disco from the 70's I later added some white LED's to mask the visual red and blue look. The aim of all this was to get plants to grow. Plants need UVA, correct?
Does UVA pass through glass, as it sits at the low end of the visual spectrum.
If not how do we manage to grow plants indoors without UVA. For example I've grown chillies/tomatoes in my house on the windowsill. Then there's green houses, Polly tunnel etc, how does UVA get in there if it's not with light to make plants grow healthy?
Help
Craig: Lots to this question and to explain glass blocking wavelengths, you need to get into band gaps and quantum mechanics. But to make it reasonably simple...

Most light bulbs, and certainly the types we use in a tortoise enclosure or our houses emit no, or extremely little, UV. LED and fluorescents are made to emit only visible light, and do not emit any UV.

LEDs emit only very narrow bands of the spectrum. When you get a blue LED, you are getting almost totally blue light only. Red is only red, etc. So when you get good color balanced LEDs they are expensive because they combine many different diodes to fill in as many color gaps as possible. Only very recently have UV emitting LEDs become available, and are very specialized. You have to specifically buy an LED made to produce UV.

Fluorescents are made to only emit visible light. The phosphors used are formulated based upon the light they will emit. Hence, you get the different color balanced fluorescent choices. Again, you have to buy specific fluorescents to get ones that are made to emit UV.

Incandescents emit a smooth, rising spectral curve. So the most of the light emitted is by far in the longer wavelengths and IR. That is why incandescents tend to be so "warm" looking. More orange and reddish in color. More in the 1500-2500K color ranges. They do emit a tiny bit of UV, but an extremely small portion of what is emitted is in this region. On the other hand they emit a great amount of their energy as near-IR. And because the glass of the bulb itself will only emit SOME UV only ABOVE 350nm, the amount of UV from an incandescent is negligible.

Plants do benefit from UV light. However, you can grow many of them without. In fact, most of the grow lights you buy don't emit UV at all. You have to look specifically for grow lights that say they emit UV light. It is specialized, and the addition of UV has been found to change the way plants grow, with better fragrances and tastes produces, etc. So the addition of UV in growing plants has value, but is something you have to purposefully provide.

SOME UVA does pass through glass. The band gaps in standard glass absorbs energy in the wavelength less than 350nm. And still filters a lot of the UV progressively above that. So light passing through a window will have some UV in it, but extremely small amounts will be left. All above 350nm. You would have to sit in front of a window in full midday sun for HOURS to just start to see the very beginnings of a sunburn!

Since tortoises have that 4th cone in their eyes, that condition is known to allow vision using UV light from 300-390nm. So some of the light that is visible to tortoises is being filtered by window glass, let alone all the UVB.

Bottom line for me... I feel we need to actively be providing specific UVA sources for tortoises kept indoors in addition to just focusing on the UVB that most are now well aware of. All of the available UVB blulbs we use do that with normally about 6 times more UVA than UVB. But once we start saying we are not going to provide UVB and rely on diet, I think it a mistake to not still provide ample UVA. Your tortoises, and plants! will thank you.
 

Anyfoot

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Craig: Lots to this question and to explain glass blocking wavelengths, you need to get into band gaps and quantum mechanics. But to make it reasonably simple...

Most light bulbs, and certainly the types we use in a tortoise enclosure or our houses emit no, or extremely little, UV. LED and fluorescents are made to emit only visible light, and do not emit any UV.

LEDs emit only very narrow bands of the spectrum. When you get a blue LED, you are getting almost totally blue light only. Red is only red, etc. So when you get good color balanced LEDs they are expensive because they combine many different diodes to fill in as many color gaps as possible. Only very recently have UV emitting LEDs become available, and are very specialized. You have to specifically buy an LED made to produce UV.

Fluorescents are made to only emit visible light. The phosphors used are formulated based upon the light they will emit. Hence, you get the different color balanced fluorescent choices. Again, you have to buy specific fluorescents to get ones that are made to emit UV.

Incandescents emit a smooth, rising spectral curve. So the most of the light emitted is by far in the longer wavelengths and IR. That is why incandescents tend to be so "warm" looking. More orange and reddish in color. More in the 1500-2500K color ranges. They do emit a tiny bit of UV, but an extremely small portion of what is emitted is in this region. On the other hand they emit a great amount of their energy as near-IR. And because the glass of the bulb itself will only emit SOME UV only ABOVE 350nm, the amount of UV from an incandescent is negligible.

Plants do benefit from UV light. However, you can grow many of them without. In fact, most of the grow lights you buy don't emit UV at all. You have to look specifically for grow lights that say they emit UV light. It is specialized, and the addition of UV has been found to change the way plants grow, with better fragrances and tastes produces, etc. So the addition of UV in growing plants has value, but is something you have to purposefully provide.

SOME UVA does pass through glass. The band gaps in standard glass absorbs energy in the wavelength less than 350nm. And still filters a lot of the UV progressively above that. So light passing through a window will have some UV in it, but extremely small amounts will be left. All above 350nm. You would have to sit in front of a window in full midday sun for HOURS to just start to see the very beginnings of a sunburn!

Since tortoises have that 4th cone in their eyes, that condition is known to allow vision using UV light from 300-390nm. So some of the light that is visible to tortoises is being filtered by window glass, let alone all the UVB.

Bottom line for me... I feel we need to actively be providing specific UVA sources for tortoises kept indoors in addition to just focusing on the UVB that most are now well aware of. All of the available UVB blulbs we use do that with normally about 6 times more UVA than UVB. But once we start saying we are not going to provide UVB and rely on diet, I think it a mistake to not still provide ample UVA. Your tortoises, and plants! will thank you.
So outside in the wilderness it is impossible to provide UVA without UVB. Is this correct?
 

Markw84

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Natural light has probably 20 times the UVA to UVB. So there is always much more A than B. Both UVA and B also reflect so it seems to be a "package deal". Natural light would contain both. On really cloudy days probably most all the UVB is filtered out but not all UVA so maybe that would be the exception where it would be possible to have A without B.
 

Anyfoot

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@Markw84

Do UVB rays pass through foliage, or does it deflect off any natural objects?
Does a tortoise have to be in direct sunlight to get UVB benefit or is it possible they can get UVB rays whilst sat in shade? Obviously dappled shade will allow UVB rays through, but this is still classed as direct sunlight I would have thought.
 

Markw84

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@Markw84

Do UVB rays pass through foliage, or does it deflect off any natural objects?
Does a tortoise have to be in direct sunlight to get UVB benefit or is it possible they can get UVB rays whilst sat in shade? Obviously dappled shade will allow UVB rays through, but this is still classed as direct sunlight I would have thought.
UVB does reflect and "bounce" off objects. Even the atmosphere reflects some that the comes at a different angle than direct. It's not a lot, about 10% of the reading in full sun will be 1-2 ft into the shade. So in the shade, near sunlight, there is still enough UVB to manufacture D3.
 
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