Scientists have harnessed the principles of nanotechnology to capture light within a dense forest of tiny carbon tubes - and the result is black from black
Most of us know that black is not really a color. Black material, or black "paint" that we buy in the store, is actually a material that absorbs most of the light falling on it. The "ideal black" is therefore a substance that absorbs all the light that hits it.
In practice there is no such material, a part of the light is always reflected. The percentage of reflected light depends not only on the type of material but also on its texture. A rough material reflects less light than a smooth material: the rougher and more porous the material, the smaller the percentage of reflected light. This is due to the fact that light that is reflected for the first time repeatedly hits the porous black material and therefore the chance that it will eventually be reflected back towards our eyes is small.
Physicists from the Rensselaer Polytechnic Institute in the USA managed to break the record and created a material that reflects only 0.045% of the light that hits it, three times less than the blackest material known so far. The secret of the physicists' success is the use of a substrate to which vertical carbon nano-tubes were attached (see photo above), a photon of light that falls into the "forest" of the tubes almost cannot get out of it. Carbon nanotubes are a clean form of carbon that has been discovered in recent years (see figure on the right). The use of carbon makes it possible to obtain a very light material, the density of the surface is only 0.01-0.02 grams per cubic meter.
Among the uses for the new material: redefining black for photographers. Today, the American Standards Institute defines black as a material whose return percentage is 1.5%. The material may also be used for astronomical detectors that want to absorb scattered light and in photovoltaic cells that turn sunlight into electricity.
17 תגובות
L.A. Ben-Ner
Still viewing the screen of any kind will not give the pure black from the screen. Because there will be returns of the light coming out of the screen to the walls of the room and back to the screen again, which reduces the intensity of the blackness of the screen, therefore the walls of the room need to be covered with a light-absorbing color to neutralize light returning to the screen
And also wear light-absorbing clothes while watching. Then we become like the pupil in the eye.
I'm trying to share this page on Facebook but I see that there is no picture and there is no summary text under the title... it's time for you to take this site into the 21st century
Another use for the color black:
A car that is painted in this color - it will not be possible to measure its speed by the speedometer
Every substance in nature, as far as we know and theoretically, absorbs electromagnetic radiation. This is how it is accepted to think today.
And now, get a riddle that is a thought experiment.
The chlorophyll molecule, let's say, absorbs light at a certain wavelength, let's call it X, and emits light at another wavelength, let's call it Y.
If we take one chlorophyll molecule and shine light on it at wavelength Y - what shadow will it make?
With the blessing of Shabbat Shalom,
Ami Bachar
straw man:
Air also has a refractive index (admittedly low) as it is a medium (material) that allows the passage of electromagnetic rays. The whole difference in this respect between the air and the ocean is in the density of the material. At least this is what I think, if in a hypothetical area in the ocean there is clear water like in a glass of water for drinking, you still won't be able to see the bottom because during the passage of the rays in some medium, they are absorbed and emitted again and again, but in this way some of the energy is transferred to the material through which they pass in the form of heat so Finally, from the depths of the bottom there will be no rays that will return.
This is just a guess:
Material that returns? It must be a mirror
Transparent material? It is a material that allows the rays to pass through it, so the less the ray breaks, the more transparent the material is (low refractive index).
And today I ask myself: if the ocean was made of a clear liquid with no refractive index at all, would I be able to see the bottom?
You are the first question I asked to understand if it is a black body absorption spectrum.
For Mickey, a transparent material absorbs a photon and immediately emits a new photon that is absorbed by the next atom so the photon progresses until it exits the transparent material, therefore, light travels at a slower speed in this material (the time from absorption to emission).
A bit unrelated but…
So there is a material that absorbs most of the light that falls on it, there is a material that reflects most of the light that falls on it, how does a transparent material "work"?
A bit unrelated but…
So there is a material that absorbs most of the light that falls on it, there is a material that reflects most of the light that falls on it, how does a transparent material "work"?
as an addition to 3
Also cover the screen with a thick blanket and you won't see that black hole at all.
It's easier to close your eyes
Webner, it seems to me that you are slightly mistaken, if it absorbs rays with shorter wavelengths than the tube, then it can effectively block radioactive radiation...
If anything then the highest theoretical energy intake the body can absorb is the length of the carbon-carbon bond. The question is whether the photon will be energetic enough to possibly break the bond, and then you will get a lump of coal that is a little less black...
To Roy
True, in general this is determined by the contrast level of the screen. Therefore, one of the considerations when buying a screen is the level of contrast (or the contrast ratio), the higher the ratio, the closer the black seen on the screen will be to the "true" black (as redefined in the article).
It should be noted that the contrast ratio is not a fixed measure between different types of screen technology (meaning between LCD and plasma for example).
Therefore, to your question, the darkest image you will see (for reference, the new material they developed) on your screen is exactly the blackest color your screen can show... (assuming you followed A. Ben-Ner's instructions)
to the point
It seems to me that the answer to your question lies in the definition of the black body, it absorbs all frequencies. Otherwise, it would not be called a black body but a green body or a blue body. Of course, the reference is to electromagnetic waves in the visible light range and probably also shorter (x-ray) and longer (infrared and radio) waves whose wavelength is small - equal to the wavelength of the carbon tubes. I don't think the cosmic background radiation (for example) is included
In this definition, its wavelength is approximately 3 cm.
To Roy
I think you are right. The screen reflects some of the light falling on it. Therefore, what you must do is as follows:
1. Lower the brightness of the screen lighting as much as possible.
2. Turn off the lights in the room and cover all the windows with lots of dark blankets to prevent light from entering.
3. Successfully.
If this is the blackest substance that exists, when I see it through the computer screen, don't I lose its "blackness"? The screen is less black than it...
What frequencies does the forest respond to?