Basics
Knowledge Base articles tagged Basics.
-
What is UVA radiation?
UVA is the long-wavelength band of ultraviolet light (315–400 nm). Learn where it sits in the UV spectrum, why ~95% of the UV reaching the ground is UVA, and how it behaves through the day, through clouds and through glass.
Read → -
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.
Read → -
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.
Read → -
What time is UVA highest? The daily curve
UVA peaks at solar noon — but its curve is far flatter than the UV Index's, so mornings and late afternoons carry proportionally much more UVA. Hour-by-hour numbers, why the shadow rule fails, and why solar noon is rarely 12:00.
Read → -
UVA on cloudy days: how much gets through
Cloud dims UVA far less than it dims sunlight — and broken cloud can briefly push UVA above clear-sky levels. Transmission by cloud type, how UVA and UVB compare under cloud, the cloud enhancement effect, and how the UVA Index models it.
Read → -
Does glass block UVA? Windows, cars and UV film
Ordinary window glass stops almost all UVB but lets a large share of UVA through. How much passes through home, office and car glass, why windshields differ from side windows, what the driver skin-cancer studies show, and how to choose UV film.
Read → -
Does clothing block UVA? UPF ratings and what actually works
UPF is erythemally weighted, so like SPF it is really a UVB measure — which is why the European standard adds a separate UVA limit. Fabric transmission by material, colour and weave, what happens when cloth gets wet or stretched, and how hats and shade really perform.
Read → -
Does UVA tan you? Tanning, burning and the base-tan myth
UVA darkens skin within minutes by oxidising melanin you already have — a tan that offers almost no protection. The three distinct tanning responses, why UVA barely burns, and what that means for tanning beds and the base-tan idea.
Read →