why ultraviolet light can be seen?

Answer 1

Ultraviolet (UV) light, also known as 'Blacklight', causes certain materials to brightly fluoresce, or
'glow in the dark'. Fluorescent paints and minerals glow brightly in vivid colors under UV light.
Many things that are invisible to the Human eye become visible under UV light


they cant be seen:) It's in an invisible part of the "electromagnetic spectrum".

Answer 2

It is indeed true that some ultraviolet light can be seen by the typical human eye. This is true for the longer ultraviolet wavelengths, but the sensitivity fades quickly at shorter wavelengths.

For the so-called typical eye (1931 CIE color standard), 555 nm appears the brightest in terms of luminance. Where the ultraviolet range starts is a whole different question, but some say below 400 nm. Based on the photopic response curve (aka ybar), the eye is about 3000 times less sensitive to 399 nm light than to 555 nm light. For 365 nm, which is the strong "longwave UV" line in mercury lamps, it takes over 140000 times as much power to be as bright as 555 nm, but it is not invisible (according to the empirical CIE 1931 standard).

Several other phenomena can easily get in the way of seeing the near ultraviolet. Fluorescence can mask it because the eye is so much more sensitive to the lower energy photons produced. Blacklights will generally also include additional wavelengths which are not in the ultraviolet range. For example, mercury lamps have a violet spectral output around 435 nm which will visually swamp the small amount of sensitivity to 365 nm. One should also keep in mind that even though you might be able to see intense ultraviolet light, it isn't healthy to do so!

There is an analogous situation at the infrared end of the visible spectrum. The first "visible laser diodes" were not like the bright red laser pointers of today. They were well into the near IR, considered outside of the visible range by most, but they could still be seen under the right conditions, in part because they were bright and because they were pure enough to not be masked by extraneous visible wavelengths.

Answer 3

Can or can't?

Humans cannot see UV light, that is why it is called Ultra (beyond) Violet, because our eyes do not have light sensitive cells that can detect them.

If you look at an UV light, it however does glow in the visible as well, that is because UV lamps are not pure UV source, they also emit some visible light as well (at the very least, this can serve to indicate the lamp is on..)

When UV light strikes an object, the energy can be captured, and returned into a reemission at a lower frequency, in the visible spectrum. This is especially true for clothings or any material that had some bleaching agent in it (washed clothes for instance, as detergent contains dyes that will absorb UV are reemit in visible, giving this whiter than white feeling that is advertised). This reemission gives the impression the object emits light on its own.

Answer 4

It can't. What you see with a blacklight is visable light.
Some objects like invisable hand stamps will absorb ultraviolet and reradiate blue, so you can see the stamp, but you're still only seeing the blue. Not the original UV.

Answer 5

Execuse me but UV's wavelength is less than 400nm an connot be seen.

Answer 6

I don't know who gave you the information that UV light can be seen but here read this:

Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. It can be subdivided into near UV (380–200 nm wavelength; abbrev. NUV), far or vacuum UV (200–10 nm; abbrev. FUV or VUV), and extreme UV (1–31 nm; abbrev. EUV or XUV).

When considering the effect of UV radiation on human health and the environment, the range of UV wavelengths is often subdivided into UVA (400–315 nm), also called Long Wave or "blacklight"; UVB (315–280 nm), also called Medium Wave; and UVC (< 280 nm), also called Short Wave or "germicidal". See 1 E-7 m for a list of objects of comparable sizes.

In photolithography, in laser technology, etc., the term deep ultraviolet or DUV refers to wavelengths below 300 nm.

The name means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the shortest wavelengths of visible light. Some of the UV wavelengths are colloquially called black light, as it is invisible to the human eye. Some animals, including birds, reptiles, and insects such as bees, can see into the near ultraviolet. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. Scorpions glow or take on a yellow to green color under UV illumination. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine of some animals is much easier to spot with ultraviolet.

The Sun emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the atmosphere's ozone layer, 99% of the ultraviolet radiation that reaches the Earth's surface is UVA. (Some of the UVC light is responsible for the generation of the ozone.)

Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths while Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm[1][2][3].

The onset of vacuum UV, 200 nm, is defined by the fact that ordinary air is opaque below this wavelength. This opacity is due to the strong absorption of light of these wavelengths by oxygen in the air. Pure nitrogen (less than about 10 ppm oxygen) is transparent to wavelengths in the range of about 150–200 nm. This has wide practical significance now that semiconductor manufacturing processes are using wavelengths shorter than 200 nm. By working in oxygen-free gas, the equipment does not have to be built to withstand the pressure differences required to work in a vacuum. Some other scientific instruments, such as circular dichroism spectrometers, are also commonly nitrogen purged and operate in this spectral region.

Extreme UV is characterized by a transition in the physics of interaction with matter: wavelengths longer than about 30 nm interact mainly with the chemical valence electrons of matter, while wavelengths shorter than that interact mainly with inner shell electrons and nuclei. The long end of the EUV/XUV spectrum is set by a prominent He+ spectral line at 30.4nm. XUV is strongly absorbed by most known materials, but it is possible to synthesize multilayer optics that reflect up to about 50% of XUV radiation at normal incidence. This technology has been used to make telescopes for solar imaging; it was pioneered by the NIXT and MSSTA sounding rockets in the 1990s; current examples are SOHO/EIT and TRACE) and for nanolithography (printing of traces and devices on microchips).

Answer 7

if you can see it,either you're not human
or it's not uv.
God bless,
gabe