Ultraviolet light is a wavelength shorter than that of visible light, but longer than X-rays, in the range of 10 nanometers to 400 nanometers. LEDs that emit ultraviolet light were introduced in 2006, and there are now ultraviolet LED flashlights available.
These flashlights are most often used to detect fraudulent documents, see watermarks, read invisible ink or investigate crime scenes. They can also be used to “fluoresce” scorpions and certain types of minerals, and charge “glow-in-the-dark” object like fishing lures.
Here are the best rated, most reliable UV flashlights available:
Update December 2015: I now recommend the Scoprio Premium — this flashlight is getting great reviews on Amazon.
Gallium Indium Nitride UV Flashlight
This Gallium Indium Nitride UV flashlight gets great ratings from Amazon buyers, so we thought we’d include it here. Reviewers were impressed by the toughness of flashlight, and the fact that it emits 365 nm UV light, which is at the very edge of our visible range. The light from this flashlight appears as a dim purple-blue to the eye, but when it shines on items that fluoresce they light up brightly.
It uses three AAA batteries — we recommend using low self-discharge AAA rechargeable batteries like Eneloop Pros in this flashlight.
Streamlight 51018 Twin-Task UV Flashlight
Streamlight is one of the few companies that still make flashlights in the U.S., and their products get consistently high ratings.
If you need reliable flashlight that provides both an ultraviolet mode and white light mode, the Streamlight Twin-Task UV Light is a great choice. It has six 390nm UV LEDs for ultraviolet light, and an ultra-bright xenon bulb for white light. It’s fully waterproof, and one meter impact resistance tested.
The Twin Task is powered by three C-size batteries — we recommend using the latest rechargeable Imedion batteries (see our full review here).
Streamlight Multi Ops Flashlight
This Streamlight Multi Ops flashlight incorporates three separate light modes. The first mode is the Ultraviolet Mode, where it uses five 390nm UV LEDs . The second mode is a red laser pointer, with a useable laser range of 100+ feet. The third mode is White LED Mode, which uses a C4 LED, producing 50 lumens of white light.
The Streamlight Multi Ops flashlight is available from Amazon for around $38.
The flashlight is powered by three AAA batteries (again, we recommend Eneloop Pros).