{"id":2115,"date":"2026-10-01T13:22:31","date_gmt":"2026-10-01T13:22:31","guid":{"rendered":"https:\/\/physicsfundamentalsinfo.com\/blog\/?p=2115"},"modified":"2026-10-01T13:22:33","modified_gmt":"2026-10-01T13:22:33","slug":"ultraviolet-radiation","status":"publish","type":"post","link":"https:\/\/physicsfundamentalsinfo.com\/blog\/waves\/ultraviolet-radiation\/","title":{"rendered":"Ultraviolet Radiation: Types & Effects"},"content":{"rendered":"\n
Definition<\/div>

\n\nUltraviolet radiation is the 100 to 400 nm region of the electromagnetic spectrum, invisible light just beyond violet, whose photons carry between 3.0996 and 12.3984 eV. Convention divides it into three bands: UVA at 315 to 400 nm, UVB at 280 to 315 nm and UVC at 100 to 280 nm. Photon energy is hc divided by wavelength.\n\n<\/p><\/div>\n\n

Stand outside on a clear day and something is landing on you that you cannot see and cannot feel. You find out about it hours later, when the back of your neck starts to sting.<\/p>\n\n

The strange part is how small the step is. At 400 nm the longest ultraviolet and the deepest violet the eye can catch carry exactly the same 3.0996 eV, yet everything shorter than that line gets filed as radiation and everything longer as light. This page follows the physics across the line: the three bands, what each photon carries, which of them reaches the ground, and where the tidy picture stops being true.<\/p>\n\n

What Is Ultraviolet Radiation?<\/h2>\n\n

Ultraviolet radiation is electromagnetic radiation with a wavelength between 100 and 400 nm: shorter than violet light, longer than X-rays, and invisible because the eye carries no receptor that responds below about 400 nm.<\/p>\n\n

The name describes a position, not a property. Violet is the shortest wavelength a person can register, and ultra-violet is whatever lies past it. Nothing about the wave itself changes at that point \u2014 it is the same oscillating electric and magnetic field that carries a radio broadcast, differing only in wavelength.<\/p>\n\n

Wavelength is what decides how much energy each photon delivers, and that single fact drives everything else on this page. Longer waves hand over less per photon; shorter waves hand over more. Our guide to the electromagnetic spectrum<\/a> lays out the full run of bands that ultraviolet sits inside.<\/p>\n\n

What earns ultraviolet its own page is where it sits. It occupies the stretch where photon energies become big enough to rearrange molecules but stay below the energies that strip electrons off atoms outright \u2014 a narrow strip, and almost every practical fact about UV follows from it.<\/p>\n\n

One habit is worth picking up straight away. If a lamp, a warning label or a study says only “UV”, the description is incomplete: a 365 nm black light and a 254 nm germicidal tube are both ultraviolet, and they do entirely different things to whatever is in front of them.<\/p>\n\n

The Ultraviolet Radiation Formula: Energy from Wavelength<\/h2>\n\n

A photon’s energy is the Planck constant multiplied by the speed of light, divided by its wavelength.<\/p>\n\n

E = h \u00b7 c \/ \u03bb<\/div>\n\n