Uv Definition and 177 Threads

Hi there, does anyone know which type of UV radiation would be most effective in polymer degradation or more importantly jet ink fading. Personally I think it should be UVC as it has the highest energy per photon but I could't find much about it so please help, it's very important as I'm behind...

Himiko has been in the news and I’d like to be sure I have the context of this correct. They can tell the light is 12.9 billion years old by how much it’s red shifted. That’s roughly 800 million years after the big bang. In that time, the universe has expanded by a factor of 8. If the light...

perhaps is a dumb quetion but, given a IR divergent integral (diverges whenever x tends to 0) \int_{0}^{\infty} \frac{dx}{x^{3}} then using a simple change of variables x=1/u the IR integral becomes an UV divergent integral \int_{0}^{\infty} udu which is an UV divergent...

hello. I am working to understand and design a UV sanitization device. What is a good resource to learn about irradiance and its relation to distance from a surface. Secondly, in real life, how is irradiance measured? Given a surface area, I would need to specify bulbs of certain...

If the primary germicidal UV wavelength is 270nm and the secondary is 254nm and I have a UV light source in air to provide germicidal effects in water, would the wavelength of the UV light source need to be 360nm and 338nm respectively assuming the index of refraction for water to be 1.33?

Hey guys, just trying to get my head around this one.. Why do UV rays effect polymer chains so much? I understand that they weaken the bonds within the chains to create free radicals which then go on to react with other things which eventually makes the whole chain degrade as a whole, but...

General query about heat absorption. We all know that something that is black both absorbs and radiates heat better. My question is how does this property vary across the spectrum, if at all, for different materials (if there is any difference?). For instance, a black painted car will heat...

Ultraviolet light can kill skin cells but infrared light only warms skin cells even though both types of lights are from the sun. Why is this, explain using the photon theory...?

Homework Statement UV light causes sunburn, whereas visible light does not. Explain. Homework Equations N/A The Attempt at a Solution I'm guessing that it might have sinething to do with the electromagnetic spectrum.

no matter what theory we use , are all UV and IR divergences of the form ?? \int_{0}^{\infty} dk. k^{m} where 'm' is an integer or there are another divergent integral different from a power-law or logarithmic divergence ?? , and another question , can be this true i^{m+n}D^{m}\delta...

Homework Statement Scientists put a lot of effort into developing suncreams which absorb the damaging wavelength of ultraviolet radiation. Suggest what might be happening to the atoms within the suncream when they absorb ultraviolet photons. Homework Equations None. This is an explain...

Do darker colored clothes offer more protection, or do light colored clothes offer more protection? I have found many answers in both.

Is there a UV lamp (not a synchrotron) that will generate UV light down to say 150 nm? I need a light source to do optical characterization (bandgap measurement as a function of temperature) of a wide bandgap semiconductor (~6.2 eV), so I would prefer a light source below 200 nm, ideally around...

http://physicsweb.org/articles/news/10/5/10/1 Zz.

What is the maximum energy a photon of UV light ( lamda= 320 nm) can transfer to an electron in a Compton collision? I used the Compton eq. and set cos= -1 and found the change in lamda to be 0.00486 nm. then using p=h/lamda where p is the momentum, i found the momentum for when lamda is 320...

Hello, I want to show my class how tonic water will fluoresce under UV light. My UV sources are a couple of 12V UV bulbs, as designed to "pimp out" (don't ask) a PC. Here's the main problem: these also put out some visible wavelength, purplish light. I'd like filter this visible light...

Hello, We have an old spectrophotometer which contains an outlet saying "printer/computer", and until now a dot-matrix printer has been attached to it. However, the printer is no longer functional, and I am thinking of interfacing an old PC to the spectrometer. The printer was attached via...

Claims universe not expanding: http://www.arxiv.org/abs/astro-ph/0509611 Another recent article about redshifts being apparently wrong: Research on candidates for non-cosmological redshifts "The paradox of apparent optical associations of galaxies with very different redshifts, the...

Is "Effects of UV Rays' a good topic in research?

I am about to purchase a devise to use for the detection of tin coating on window glass. I am a glass artist who fuses glass in a kiln. I know that, in the manufacturing process of the window glass, a tin coating is applied to one side . For my work, I need to know which is the tin coated...

Howdy, i was wondering is anyone knows how a UV-visible spectroscopy works and how it differs to a double beam scanning spectrophotometer? i know that UV visible spectroscopy needs a radiation source that is passed into a silt and then in a monochromator but how do u know how to...

Does anyone know the range of the wavelengths of the UV light that reaches the Earth (ground)?

In another thread there's a discussion of the wavelength limits of the human visual system. A question has arisen re the damage that UV can have on the eye; specifically by wavelength and intensity. Can anyone help? There's tons of material on the internet, but how to judge what's...

The big news of the day, seems to be that tanning beds have addictive properties. Clients choose tanning beds that have some UV light to offer, because it gives them an "addictive", sense of well being. The real news is this. Due to scares regarding skin cancers, and due to the fact that...

So I have an chem assignment which I've been going through for the past week or so, but the last question has provided somewhat of a stumbling block. Here it is, So from the question, I have gathered the following, High pH solutions absorb at higher wavelenghts. Whereas low pH solutions...

hello all i'm investigating the band gap of certain nanocrystallites in the powder form, using a Shimadzu spectrometer with the powder dissolved in ethanol. The spectra, however, come with several peaks in addition to the expected peak for absorption. This is not unexpected as transitions to...

This is an unusually important question. Could one determine the approximate age of a manufactured bismuth/magnesium/zinc composite somehow by the effects of UV, cosmic rays, or some other type of energetic particle acting on the material? For example, by microscopic examination or by some...