Fluorescent colours and the atmosphere

[tishk]

Hi guys. I'm an anthropologist really, and won't pretend I know the finer points of physics. still, this thing bothers me, and hopefully someone on this forum thinks it's an easy question.

I noticed a while back that local crafts in highland cultures - Himalayan and Andean alike! - made use of Day/Glo, neon, fluorescent colours. I think I have figured out that there is more UV light in high altitudes due to thinner atmosphere, although I don't seem to have very good sources for it. If anyone has read anything that could be used as a respectable reference, make my day.

The question that perplexes me, tho, has to do with how, while the general idea for observing fluorescence without a blacklight seems to be to conduct the experiment at noon and in direct sunlight (e.g. http://www.ucar.edu/learn/1_5_2_23t.htm), the recommended use of high-visibility materials in poorly lit situations (e.g. http://www.ipmba.org/reviews/The_Nee...ty_Apparel.pdf ) indicate that there is enough uv/light to bring about an "almost magical" fluorescence also at dusk and dawn.

Could you point me to an article or two that helps explain away this apparent paradox? or a thread in the forum, at that. This one, e.g., was close to answering my question... https://www.physicsforums.com/archive.../t-123480.html

 

[AndyW]

Hi there,

I can provide some insight into your question about the use of fluorescent colors in highland cultures. First of all, you are correct in your observation that there is more UV light in high altitudes due to the thinner atmosphere. This is because the atmosphere acts as a filter, absorbing and scattering much of the UV light. At higher altitudes, there is less atmosphere to filter out the UV light, so more of it reaches the Earth's surface.

As for your question about the paradox of using fluorescent colors in poorly lit situations, there are a few factors at play here. First, it's important to note that the UV light from the sun is not the only source of UV light. There are also artificial sources of UV light, such as fluorescent bulbs and blacklights. These can also cause fluorescence in materials that are designed to react to UV light.

In poorly lit situations, there may not be enough visible light for the fluorescent materials to be seen by the naked eye. However, there may still be enough UV light present to cause fluorescence. This is why high-visibility materials are recommended for use in these situations - they are designed to reflect UV light, making them visible even in low light conditions.

Additionally, the time of day can also affect the amount of UV light present. At dusk and dawn, the angle of the sun is lower, meaning that the UV light must travel through more atmosphere before reaching the Earth's surface. This can result in less UV light reaching the surface compared to the middle of the day, but there is still enough to cause fluorescence.

I hope this helps to explain the apparent paradox you observed. As for articles or threads that may provide more information, I would suggest looking into the physics of fluorescence and UV light, as well as studies on the use of fluorescent colors in highland cultures. I hope this information is helpful to you.

 

[sir-pinski]

Hi there, as a physicist, I can offer some insights into your question about fluorescent colors and the atmosphere. First, let's clarify what fluorescence actually is. Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. In simpler terms, when a fluorescent material is exposed to light, it absorbs some of that light and then re-emits it at a different wavelength, giving off a bright, glowing appearance.

Now, to address your question about the use of fluorescent colors in high altitude cultures. You are correct in thinking that there is more UV light present at higher altitudes due to the thinner atmosphere. This means that there is a higher chance for fluorescent materials to absorb UV light and re-emit it at a visible wavelength, making them appear brighter and more vibrant.

As for the paradox you mentioned, it is important to note that the intensity of UV light at dawn and dusk is still significantly lower than at noon. However, it is enough to activate the fluorescence in materials that are designed to be highly visible in low light situations. This is why fluorescent materials are often used in safety apparel for workers who may be working at dawn or dusk when the natural light is low.

In terms of sources, you may want to look into articles on the absorption and emission spectra of fluorescent materials, as well as studies on the effects of UV light on different altitudes. I hope this helps to clarify the connection between fluorescent colors and the atmosphere. Best of luck in your research!