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23

You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-A was (and still is) used in tanning beds due to its perceived safety over UV-B. However, a lot of research has been done since. UV-A is well understood now ...


13

You will be interested in Aphakia, which is the lack of an eye lens usually through surgery but sometimes from birth. These individuals supposedly see UV as a whitish-blue or whitish-violet: This appears to be because the three types of colour receptor (red, green and blue) have similar sensitivity to ultraviolet, so it comes out as a mixture of all ...


6

The CDC's disinfection guidelines lists UV radiation between 328 and 210nm as effective for disinfection, with a maximum of bactericidal activity occurring between 240-280nm. At this wavelength DNA damage (Thymine dimers) is induced with a high rate. Due to practical reasons UV light is mostly used to disinfect water, if used in rooms there is some ...


5

There are (at least) two sides to this story. One is direct DNA damage being caused by UV-B light which happens to have photons with just the right amount of energy to interact with thymine. This has been known, and assumed not just during the 80s, but until the late 2000s to be The One major thing that causes cancer, or trouble in general (there's papers ...


4

Our skin contains quite a lot of water and I think this is answers the question: The absorption of UV light by this water goes drastically up when you shift to shorter wavelengts with a minimum absorption in the UV-A spectrum. See this figure (from here): So water has a very low absorption around 340-350nm (UV-A) and a very high absorption at shorter ...


4

First to address some of the comments: Concentrated UV damage does hurt your skin, it's called sunburn. Lighter amounts of UV damage can cause cancer over time. UV damage can be "felt", as can photonic pressure in extreme cases. The issue at hand is "what is detection." Back to your eyes: As addressed in this answer, the human retina is able to detect ...


3

Behar-Cohen et al. notes the periphery of the cornea has a focusing effect: UVR incident from the periphery is refracted into the eye, and due to the focusing effect of the cornea, UV radiation is on average 22-fold stronger at the nasal limbus, which is the typical site for pterygium and pinguecula. Moreover, UV radiation is on average eight times ...


3

The damage to your eye does not only come from UV exposure, but also from infrared (IR) radiation. Your eye contains a lens that focuses the incoming rays to a narrow point. This point would get very hot if you looked directly into the sun. This is comparable to focussing the sun on a piece of paper with a magnifying glass, it would start to burn. Also, the ...


2

Yes. Natural sunlight doesn't have a good substituent. Melatonin levels and circardian rhythms are directly affected by natural sunlight. As far as LEDs goes, a french study concluded that blue light may have photochemical risks and affect our retina. Source http://www.ledinside.com/knowledge/2014/4/...


1

You can make homemade bacterial growth medium. https://www.madaboutscience.com.au/shop/science-extra/post/grow-bacteria-on-homemade-agar-plates/ Basically it is just nutrient jello: beef stock, sugar, gelatin to make a firm surface. It would be nice to have all your cultures in uniform plates or cups. You could order petri dishes or use what you have ...


1

You should have a look at wikipedia > melanin. Melanin is a broad term for a group of natural pigments found in most organisms. [..] Melanin is an effective absorber of light; the pigment is able to dissipate over 99.9% of absorbed UV radiation.1 Because of this property, melanin is thought to protect skin cells from UVB radiation damage, reducing the ...


1

The wavelength of UV-C most effective at provoking mutagenesis in DNA is 260 nm, which has been shown to kill Cryptosporidium parvum at doses below 10 mJ/sq cm. http://www.ncbi.nlm.nih.gov/pubmed/12834745 In units of lux, 10^5 lux of sunlight has been shown to kill 99.9% of Aeromonas salmonicida after two hours of exposure. http://www.sciencedirect.com/...


1

UV Rays kill the cells by damaging the DNA. UV lights do not disrupt the cell membrane. If a cell is exposed to UV light, it creates THYMINE dimers (bond). Thymine dimers are the actual disruption in the kinks of DNA. UV exposure to skin is proportional to the cell damage. P53 is a gene product which takes care of fixing cell damage. However it has a ...


1

Some physical methods of sterilisation are in hospitals Steam autoclaving Dry heat – thermostat White light / UV light sterilization where continuous UV light has poor penetration. UV radiation heat is absorbed by proteins and nucleic acid. All micro-organisms contain tehm. They inactivate the DNA. There will be electronic and photochemical reactions ...


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