Which UV band has the shortest wavelength?

• A. UVA
• B. UVB
• C. UVC
• D. Visible

Answer: (C)

The shortest wavelength in the ultraviolet range sits at the high-energy end of the spectrum. Ultraviolet light is divided into bands by wavelength: UVA is the longest within UV, UVB is shorter, and UVC is the shortest. Specifically, UVA runs roughly 315–400 nanometers, UVB about 280–315 nm, and UVC about 100–280 nm. Because wavelength decreases from UVA to UVB to UVC, the UVC band has the shortest wavelengths of the UV categories. The visible spectrum starts around 380–400 nm and extends to about 700 nm, which is longer than UVC, so it isn’t the shortest. (Atmospheric ozone blocks most UVC from reaching the surface, which is useful context for why exposure to UVC is less common outdoors, even though it has the shortest wavelengths.)