Or "UV lights" appear purple!! Ultra violet light is invisible, isn't it?
2006-11-14 09:57:33 · 3 answers · asked by Link 4 in Science & Mathematics ➔ Physics
UV lights appear violet. This is because the light generated is not pure UV, but rather is spread around the UV part of the spectrum. Some of it is UV (and invisible) and some of it is at the very edge of the visible range (violet) which is the part you see.
For devices that require aiming this is useful so that you can see where the light is going instead of having to guess.
2006-11-14 10:04:52 · answer #1 · answered by Lem 5 · 3⤊ 0⤋
The idea is that the setting catalyst (a photo initiator) contained in the dental composite is sensitive to and activated by this particular color (wavelength) of light.
The "traditional" visible spectrum runs from red to violet. Red light has the longest wavelength and violet the shortest. Light which has a longer wavelength than red is called infrared, and light which has a shorter wavelength than violet is called ultra violet or UV. The wavelength of light is measure in units of nanometers (abbreviated as nm), and 1nm is a billionth of a meter (that's a US billion or 1000 million, not a UK billion which is a million million!). Light shorter in wavelength than about 400nm is called ultra violet.
2006-11-14 18:11:37 · answer #2 · answered by Elisha 3 · 1⤊ 0⤋
You are correct. But the light source isn't perfect. Most of its energy is in the ultraviolet, but some is still in the visible spectrum.
2006-11-14 18:03:57 · answer #3 · answered by Frank N 7 · 1⤊ 0⤋