The World in UV
5,362,915
Published 2018-07-21
The Physics Girl looks at sunscreen: • SUNSCREEN in UV
How to make sunscreen from scratch: • How to Stop the Sun from Killing You
In summary, ultraviolet light interacts differently with matter for a number of reasons:
1. Some pigments selectively absorb UV so they may appear white in the visible but dark in the UV. The pigments usually dissipate the UV energy as heat, though the breaking of bonds can also occur.
2. Fluorescent molecules absorb UV light and re-radiate that energy as visible light. This makes them look dark in the UV but glowing under black light.
3. Ultraviolet light scatters more than visible light because the wavelength is shorter and Raleigh scattering is proportional to the reciprocal of wavelength to the power of four.
Special thanks to HHMI BioInteractive for their awesome animations of melanocytes and how the melanin in melanosomes protect your DNA. To see the full video explaining how we get our skin color, check out: • How We Get Our Skin Color | HHMI BioI...
Special thanks to Patreon supporters:
Donal Botkin, Michael Krugman, Jeff Straathof, Zach Mueller, Ron Neal, Nathan Hansen, Yildiz Kabaran, Terrance Snow, Stan Presolski
References:
Overview of main UV effects:
Visualizing Rayleigh Scattering through UV Photography
journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-14-002…
Arctic animals are photographed in the UV to increase visibility and get an accurate count:
Lavigne, D. (1976). Counting Harp Seals with ultra-violet photography. Polar Record, 18(114), 269-277. doi:10.1017/S0032247400000310
Absorption spectrum of melanin: www.cl.cam.ac.uk/~jgd1000/melanin.html
"The spectroscopy of human melanin pigmentation," by N. Kollias. In: Melanin: Its Role in Human Photoprotection, pp. 31 - 38. Valdenmar Publishing Co. (1995).
"Optical properties of human sclera, and their consequences for transscleral laser applications," by A. Vogel, C. Dlugos, and R. Nuffer, Lasers in Surgery and Medicine 11(4), pp. 331 - 340 (1991).
"The incidence and time-course of latanoprost-induced iridial pigmentation as a function of eye color," by P. Wistrand, J. Stjernschantz, and K. Olsson, Survey of Ophthalmology 41(S2), pp. S129 - S138 (1997).
Music by Epidemic Sound: www.epidemicsound.com/ "Spring Moods 5"
All Comments (21)
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6:00 - I always wondered how scientists flirt with each other... I guess that's a question answered now. "Your skin looks so good in the visible spectrum of the light"
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Sunscreen companies should do this as an ad. I would have been WAY more likely to use it as a kid if I could see that it actually does anything.
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if you want to get rid of the fog just turn up your render distance
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After losing the lens from one eye after surgery (and none was implanted), I discovered how much more I could see into the near UV. A common fluorescent "black Light" tube is barely visible in daylight with normal vision. With my "lensless" eye (and a contact), I could easily see a lighted tube as a purple-white glow from tens of feet away in full outdoor daylight.
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- Son, did you apply the sunscreen? - ...yes, mom! turns on the UV camera
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talking to a girl "You're so beautiful... just not in the UV spectrum"
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What I find particularly fascinating is that if we could see UV light we would most likely also see colours there. This would of course only be the case if we had multiple photoreceptors for different UV wavelengths but it is still quirky to think that colours are actually just illusions.
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This actually shows me how well sunscreen actually works.
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I wanna be as happy as he was when the soda started bubbling
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"How do I put this..." at 6:05. Nice Derek, nice.
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8:10 dude looks like he's covering himself in mud to not get detected in a covert mission in Nam
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At 1:33 - the 'haze' with a UV camera is a great demonstration of why the sky is blue. It's showing that the UV light refracts more than the lower frequencies, and since the blue/violet spectrum of visible light is the highest frequencies, they scatter more. A UV camera isn't picking up those lower frequencies, so it can't see anything through the 'haze'. :) *edited for spelling because autoderp*
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Will enough UV exposure cause heavy damage to the skin? Or will it only cause... light damage?
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Great video and thanks for the shout out! I was wondering why our UV footage at Death Valley was so hazy in the distance, now I know why!
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Miss you PhysicsGirl, I hope you feel better soon
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it's hard to wrap my mind around birds being able to see in ultraviolet as well as normal color vision...
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In an alternate universe: 'The World in Visible Light" - "Why is visible light so clear compared to our normal hazy atmosphere?"
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I'd love to see a video like this for infrared as well
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8:00 How long until mobile phone cameras have a UV mode to check how well you've applied sunscreen! This could save a lot of skin cancer issues.
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UV and visuvals clearly explained. I love this video for its simplicity and clarity about UV .
