what exact physics or chemistry is behind making a material/object transparent or transluscent or opaque?
413143
For solids, it's the electronic structure.  Are there energy levels for the electrons that match the energy of visible light?  If not, there is nothing for visible light to be absorbed by, and the object is transparent.  If such energy levels do exist, they will absorb the light whose energy corresponds to the difference in energy levels.  So, if there are energy levels corresponding to light with a wavelength from 600-700nm, the object absorbs red light and will let through or reflect green and blue.  \n\nFor some composite solids and for liquids, there isn't such a defined electronic structure.  Here, it usually depends on the sizes and densities of particles suspended in the object.  Milk, for instance, is opaque because the particles in it are the right size for light to get bounced all around in it, thus losing its original path.  In these cases, the object acts more like a fog, albeit a very dense one.
49474
the current model of light recognizes the dual nature of light which depicts how light displays both properties of waves(ex: interference, diffraction, diffusion, refraction, etc.) and properties of matter(ex: photoelectric effect).  The reason for this is that although light does consist of waves, it also consists of tiny packets of energy called photons which occasionally display properties of matter.
218232
light has dual nature when light interacts with matter it behave as a particle but when light propagated through media  it behaves like waves intefrnece reflection and refraction
1053154
Ordinary glass is transparent to visible light due to an absence of electronic transition states in the range of visible light, and because ordinary glass is homogeneous on all length scales greater than about a wavelength of visible light. Ordinary glass partially blocks UVA (wavelength between 400 and 300 nm) and totally blocks UVC and UVB (wavelengths shorter than 300 nm) due to the addition of compounds such as soda ash (sodium carbonate).\n\nPure SiO2 glass (also called fused quartz) does not absorb UV light and is used for applications that require transparency in this region, although it is more expensive. This type of glass can be made so pure that, when made into fibre optic cables, hundreds of kilometres of glass are transparent at infrared wavelengths. Individual fibres are given an equally transparent core of SiO2/GeO2 glass, which has only slightly different optical properties . Undersea cables have sections doped with erbium, which amplify transmitted signals by laser emission from within the glass itself. Amorphous SiO2 is also used as a dielectric material in integrated circuits, due to the smooth and electrically neutral interface it forms with silicon.
1135706
An object that absorbs all the light that falls on it, then it is called a "blackbody". If an object allows all light that falls on it to pass through unimpeded, then that's an "invisible body".
53724
Pure water is transparent and can not change the color of a cloth.  However, when light (photons) enter say blue cloth all the wavelengths that are not blue are absorbed and the blue is reflected.  However, these blue photons are diffused through the cloth.  Adding water allows the photons to interact with water molecule electrons and escape unchanged much easier to your eye and the true color of the cloth dye becomes apparent and darker.  It is also true that when you mend cloth the thread you use only needs to be a close color match (not identical).  A single thread is too small to reveal its true color and will blend (and become overwhelmed) with the overall cloth color.  Notice that white paint does not get darker when wet with water.  All photons (every wave length) are still reflected.
419751
One is more opque than the other. The cardboard lets no light through while the plastic sheet is somewhat translucent.  Translucent means that some light will get through.  Opque items are denser materials and therefore let less light through if at all.  Translucent is the opposite.  Hope that this helps.
1004069
Ignore the above answers they are all horribly wrong. This is a chemistry question.\n\nColors in chemistry are due to two main phenomena. \n\n1. Light Absorption\n2. Charge Transfer\n\n\nFor the first case an electron can be promoted to a higher energy state by absorbing light energy. White light consists of wavelengths (about) 400-800 nanometers. Wavelength is inversly related to frequency which is related to the energy of light. The photonic energy of the light from certain wavelengths is absorbed to promote an electron. The rest of the light is transmitted. This transmitted light is what we see. But also keep in mind that the eye works strangely and we see mixed colors a little different.. I dont know why but just keep it in mind.\n\nThe second phenomena is charge transfer. This occurs when  an electron is transferred from one atom to to another. An example is KMnO4 (which has no d electrons) but is purple! This is because a electron is transferred from the oxygen to the manganese. \n\nAnd there are some other mechanisms for which colors are produced. One of the latest is now understood by a physics professor at ucla. Hes been studying how sound can interact with a bubble to produce light.
335985
Hi there,\n\nTemperature vs colour goes red, orange, yellow, green, blue, violet. It is simply the spectrum of light (think rainbow) because that is what it is based on.\n\nSo red light is actually the coolest, and as you go up the temperature scale, you run through the spectrum to violet.\n\nWhite light is a combination of ALL the different colours of light, so something which glows white hot is just releasing all different levels of energy, so it appears white. So in actual fact, blue (or more accurately violet) is hotter, because if something is blue hot, then it is releasing ALL really high levels of energy, but you rarely get anything which is completely blue hot - there is almost always some sort of mixture, and usually, the object glows white tinged with blue (which just means that the object is releasing all different levels of energy, but predominantly or mostly blue!)\n\nJust for your interest, the way this works is, when you heat something up, you are exposing it to invisible energy called "infra red" which is just heat. So when you touch something and it feels hot, you are simply sensing infra red energy!\nThis energy is "weaker" than light (so light is actually more energetic than heat), but if you let an object get hot enough, it stops being able to release the heat as just infra red and starts to release it as visible light. The hotter the object gets, the further along the spectrum is the light emitted.\nActually, if the object absorbs enough energy it will start to release Ultra Violet (UV) and X-Rays!
382910
If the energy of the light does not correspond to the difference in two energy levels in the atoms it hits, the light will pass through. The vast majority of photons are passed through the glass this way. The rest are reflected at the surface or absorbed and dispersed.
277381
on some machines, the transparency doesn't work with the background-color\ntry it with just background.\n\nbackground: transparent;
1034438
I suppose we could find some sort of clear plexi-glass type of material that would be suitable for aircraft-grade structures, but making the entire plane clear would probably be impossible.  A materials science engineer would probably know more about this.\n\nOne question from me though: is there a need for this?  The stealth bomber, for example, flies so high that visual detection by ground based anti-aircraft emplacements is quite low.  So low, in fact, that I have heard that it has never been fired upon from the ground (don't quote me on that though).  So for modern military aircraft applications, I would say radar invisibility is far more important than visual invisibility.\n\nAs a side note, I had read about a clothing-like light scattering material in either Popular Science or the Spectum magazine (forget which).  Anyway, it somehow bends or scatters light in such a way as to partially reveal what is behind the covered object.  There was a picture of a guy wearing a piece of it, and I was pretty amazed.  It was far from perfect (could still obviously see the guy), but I could imagine it being a very useful camo material if it improves.
974284
I certainly hope you have visited the link below for visual and mathematical insights into this problem.\n\nHowever, the only materials that come to mind which lend themselves to a physical model of this transformation are:\n\n o thin-but-rigid springs or "lead" wire(s) as supports/frames\n o plastic wrap as a surface substrate\n o flexible, rubberized, quick-drying paint as a protective layer\n\nI regret that my imagination is limited with respect to this problem, but good luck with your project!
45176
it allows some light to pass through it, or "conducts" light...it DOES NOT DIFFUSE LIGHT by definition.  a perfectly clear window is translucent, and so is a stained glass window. is not the same a transparent though, because it does not necessarily allow all frequencies of light through,
983408
There has been some sucess in invisibility lately and the real deal for governments is just around the corner.\n\n\n\nInvisibility Achieved \nInvisibility Achieved ... New Scientist - Working invisibility cloak created at last. Photonics Online - First Demonstration of a Working Invisibility Cloak ...physics.about.com/b/a/007455.htm \n\n\nen.wikipedia.org/wiki/Invisibility\nInvisibility is here, just not perfected. Since objects can be seen by light in the visible spectrum from a source reflecting off their surfaces and hitting the viewer's eye, the most natural form of invisibility (whether real or fictional) is an object which does not reflect nor absorbs light (that is, it allows light to pass through it). In nature, this is known as transparency, and is seen in many naturally-occurring materials (although no naturally-occurring material is 100% transparent).\n\nVisibility also depends on the eyes of the observer and/or the instruments used. Thus an object can be classified as "invisible to" a person, animal, instrument, etc.\n\nInvisibility \nThe following text is a combination of two separate files on Invisibility. ... Cold-rolling of steel - To induce Invisibility in matter, we can use any of ...www.keelynet.com/unclass/invisi.htm  \nThe US government has a cloat of invisibility but it is not yet feasible for say a tank or battleship.\nHere's how to make an invisibility cloak - Science - MSNBC.com \n... on new types of materials that can throw a cloak of invisibility around objects. ... engineer Nader Engheta, who published his own invisibility recipe last year. ...www.msnbc.msn.com/id/12961080?GT1=8199
775142
All materials have what is called a "refractive index" which is determined by the speed at which light travels through. This is similar to how the speed of sound varies between materials (hard wood vs air). \n\nThe speed of like that you state, 3*10^8 m/s is the speed of light in a vacuum, and only a vacuum.\n\nThe reason the speed of light varies between materials is how light interacts with the atoms in these materials. You see, the way light travels through materials is by getting absorbed by atoms and re-emitted. The energy of an atom rises temporarily. As the energy falls again, the photon is re-emitted out the atom.\n\nThe amount of time it takes for an atom of a substance to do so determines how fast light travels through that substance. This is because the light is just getting absorbed and emitted to be absorbed by the next atom, in a chain!\n\nThis difference in speed accounts for why materials refract light. Without this property, eye glasses, lenses, etc won't work. It is also why things in the water appear distorted etc.\n\nIn a vacuum, however, we cannot change the speed of light, it is a constant.
986686
It is how opaque a material is.\n\nIt is measured by how much light can be seen through the material.