UV LEDS are really "near UV" @ 395, 410 and 420 nm. Real UV is considered less than 370 nm.

Advanced UV LEDs are @ 255, 265, 270, 280, 285, 290, 300, 310, 320, 330, 340, 351, 360, 370, 375, 393, 395, ,  nm.

See:

http://www.roithner-laser.com/LED_diverse.htm

nm=nanometer the unit of measurement of wavelength.

"Shortwave" type UV discharge lamps use external filters and come in at 254 nm. SW-UV will burn your eyes.

"Longwave" discharge lamps use blue dye on the bulb (BLB) and are around 365 nm. BL versions have no blue filtering, give more UV, but also give some visible light. LW-UV is what the kids use to light up those posters. toys etc.

There is also a Mid-Wave at 312 nm.

The UVC lamps are the germicidal types, very dangerous @ 200-280 nm.

Wavelength

The distance between two points on a wave which have the same value and the same rate of change of the value of a parameter, for example, electric intensity, characterizing the wave. The wavelength, usually designated by the Greek letter λ, is equal to the speed of propagation c of the wave divided by the frequency of vibration f; that is, λ = c/f .

Fluorescence = The emission of electromagnetic radiation, especially of visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued.

Phosphorescence  = A delayed luminescence, that is, a luminescence that persists after removal of the exciting source. It is sometimes called afterglow.

Luminescence =

Concept

Luminescence is the generation of light without heat. There are two principal varieties of luminescence, fluorescence and phosphorescence, distinguished by the delay in reaction to external electromagnetic radiation. The ancients observed phosphorescence in the form of a glow emitted by the oceans at night, and confused this phenomenon with the burning of the chemical phosphor, but, in fact, phosphorescence has nothing at all to do with burning. Likewise, fluorescence, as applied today in fluorescent lighting, involves no heat—thus creating a form of lighting more efficient than that which comes from incandescent bulbs.