UVA Knowledge Base
Short, plain-English guides to ultraviolet A radiation — what it is, how it differs from UVB, why it matters for your skin, and why the familiar UV Index doesn't tell the whole story.
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What is UVA radiation?
The long-wavelength (315–400 nm) part of ultraviolet light: where it sits in the spectrum, why it dominates the UV that reaches the ground, and how it behaves through the day and through glass.
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UVA vs UVB: what's the difference?
Wavelength, how deep each penetrates skin, sunburn vs photoaging, vitamin D, clouds and glass — a side-by-side comparison of the two UV bands that reach Earth's surface.
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The dangers of UVA radiation
Photoaging, indirect DNA damage, skin cancer risk, eye damage and immune suppression — what the research says about UVA's quieter, longer-term effects, and how to reduce exposure.
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What the UV Index measures — and why we need a UVA Index
The UV Index is weighted for sunburn, so it's dominated by UVB and under-represents UVA. Here's what it does and doesn't capture, and why a dedicated UVA measure is useful.
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