Ultraviolet light is just past violet — higher energy than visible light. It causes sunburn and damages DNA.
Quick check
Ultraviolet light gives you sunburn but infrared doesn't, even though infrared can feel hotter. Why?
Just past violet
UV is the slice of spectrum between visible violet and X-rays. It's split into UVA, UVB and UVC by wavelength — UVC is the most damaging, but the ozone layer absorbs nearly all of it before it reaches the ground.
Sunscreen works by absorbing or scattering UV before it reaches your skin. 'SPF 30' means it takes ~30× longer to burn — it does not mean 30× 'stronger'.
UV at work
- Vitamin D synthesis in skin.
- Sterilising water and surfaces (UVC kills microbes).
- Fluorescent 'black light' posters and forensic checks.
- Curing dental fillings and gel nail polish.