Comparisons
Knowledge Base articles tagged Comparisons.
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UVA vs UVB: what's the difference?
UVA vs UVB compared: wavelength, how deep each penetrates skin, sunburn vs photoaging, vitamin D, skin-cancer roles, and how clouds, glass, time of day and season affect each.
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The UV Index scale explained — and what it leaves out
What the UV Index numbers mean, where the 0–11+ scale comes from, the WHO band colours and advice, how high it can actually go — and the erythemal weighting that makes it under-report UVA.
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UVA and vitamin D: all of the cost, none of the benefit
Vitamin D synthesis is driven by a narrow slice of UVB around 295–300 nm and stops entirely below 315 nm. UVA produces none of it — which makes winter sun, window light and sunbeds pure exposure with no return.
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