When I measured the sun, it gave a UV index of 6. When I measured the uv flashlight, it gave a uv index of 196. Is the sun not more powerful in UV than the flashlight?
In: Physics
UV Index of 196?! Probably your meter is bad…
There are 3 types of UV radiation based on their wavelength. [UVC, UVB, and UVA.](https://www.hepacart.com/hubfs/03-Images/Blog/UV-ForceAirQuality_UVDifference.jpg#keepProtocol) UVC is entirely absorbed by the atmosphere around the earth, UVB is partially absorbed, and UVA relatively passes through (all are absorbed to some extend, I’m talking relative to each other).
Typical UV flashlights are only submitting UVA, the higher wavelength UV radiation at 365-380nm, while UV Index focuses much more on the shorter wavelengths (UVB) as they are responsible for sunburn (not entirely true because the shorter wavelengths of UVA also cause sunburn, but for simplicity lets go with this).
UV Index is [weighted across its power spectrum](https://en.wikipedia.org/wiki/Ultraviolet_index#/media/File:Erythemal_action_spectrum.svg) based on the Erythemal action spectrum (how sensitive the skin is at a certain wavelength of light – ie. sunburn sensitivity).
UVA is weighted just very very lightly because its not very damaging compared to UVB.
There is no way that a UV Flashlight would be giving you a UV Index of **196** as it only gives out UVA light of a longer wavelength which does not cause any meaningful skin reaction. **Either that, or you have a UV-C Flashlight which you should destroy and throw away because that’s a dangerous device and NOT A TOY.**
When I take my calibrated UV Index meter into the sun I tend to get exactly the same measurements as weather stations. When I stick it against a powerful UV light for reptiles, it spikes to 13-15 which is absurdly high. My UV Flashlight doesn’t register, and it’s a 2W UVA flashlight.
I can guarantee you that unless you have a powerful UVB source and you meter it very close to it, the sun is more powerful, certainly around the tropics where you get a UV Index of 10-11 at ~sea level.
For reference at a UV Index of 15, you can end up with skinburn in as little as 7 minutes exposure. You can reach that when you are high up in the mountains at clear sky around the equator. And while exposure time doesn’t drastically go down further by a higher amount of UV radiation, 196 is very very extreme. So I hope your measuring device is broken and you are not messing around with a potentially dangerous UV source.
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