You should look at it the other way round. The word 'ultra' means 'beyond', so you have the visible spectrum which ends at violet, then what is beyond is 'ultra violet'.
No, the human cannot see ultraviolet rays with the naked eye.
It doesn't look anything. The human eye can't see it at all. You can't even tell if ultraviolet light is there or not.
infrared light and ultraviolet light
No, the visible part is called visible light. Ultraviolet is invisible to the human eye.
No, the visible part is called visible light. Ultraviolet is invisible to the human eye.
the lens is the most sensitive part of the eye. the retina can become damaged when there is an excessive ultraviolet light exposed.
ultraviolet light
No. Normal human eyes are unable to see ultraviolet at all. People with aphakia say it looks pale blue. The author of this answer says it looks yellow but may be unique in this perception.
"Color" is the sensation that a light produces in your eye and your brain. Ultraviolet light is not detected by your eye, so there's no such thing as its color.
Violet, after that comes ultraviolet that the human eye cannot see.
It is not visible by the naked eye.
A true "black light" should emit only ultraviolet radiation. Violet light waves have the highest frequency visible to a human eye. Ultraviolet has a higher frequency, and the human eye cannot detect it. When you buy a "black light" at the party store, in addition to the ultraviolet radiation, the bulb will usually give off violet light as well (analogous to a yellow light bulb looking a bit orange). You can see the violet light, but it's really the invisible, high energy ultraviolet light that provides all the "cool" effects.