Yes, ultraviolet is technically outside the visible range (ultra meaning too short a wavelength). In the same way that infrared wavelengths are too long for us

Yes, ultraviolet is technically outside the visible range (ultra meaning too short a wavelength). In the same way that infrared wavelengths are too long for us to see. In optics, basically anything beyond blue is referred to as UV until you get to other stuff like X-ray. The reason is partly laziness and partly that there aren't many functional uses for violet light, whereas UV is used for all sorts of things. There are several different classes of UV light, just like there's many shades of blue or classes of infrared (near, long-wave, mid-wave, etc). The reason that you can see light from "UV" lamps is because they're usually emitting over a range of wavelengths and some of that falls in the visible spectrum. And on the other end, some infrared LEDs emit a little bit of red light which is visible. If something isn't visible it matters for safety. Most of your eyes' defense mechanisms rely on limiting the amount of light entering your pupils, so they need to be able to perceive how bright a light is. Strong UV is particularly dangerous because it's high energy (think sunburn) and you can't see it so you won't reflexively blink and your pupils won't close. Infrared can also be dangerous, but it's a lower wavelength so you need more of it to do damage.