Why does plastic absorb infrared radiation?
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Most plastics are made of organic compounds.  The inter-atomic bonds of organic chemicals have quantum energies that correspond precisely with the energy levels in the infrared region of the electromagnetic spectrum.  \n\nIf you irradiate an organic chemical with IR, it will absorb quanta of IR energy that correspond to specific vibrational energies in the molecule -- this excites the bond and makes it vibrate more rapidly and with greater amplitude.  By scanning across the entire range of IR frequencies, you get a "fingerprint" of absorptions that can help to identify the nature of the organic chemical being scanned.\n\nThat's it in a nutshell -- I hope it helps.  There are lots of instrumental analysis books available that will explain it in more detail.
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IR ray is an electromagnetic wave, like visible light, X-ray, gamma ray and UV ray(even radio waves). the energy of IR wave is lower than visible, UV, X-ray and gamma. when one of the high energy electromagnetic waves hit a molecular, they will brake it to smaller parts( if they have enough energy) but IR doesn't have enough energy, so all it can do is to make the molecules move faster. the movement average of molecules is what we call heat, so when IR hits a material, it'll rise the average molecular movement in it and we say that the material became hotter.
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When sunlighht is reflected at a significant angle from a surface the reflected light tends to be partially polarized, meaning that one of the polarization directions of the light is more strongly reflected than the other (which is either transmitted or absorbed by the surface).\n\nA polarizer is an optical element that transmits only one polarization of the light and (depending on the type) either reflects or absorbs the other polarization.  The polarizers in polarized sunglasses use a plastic film that absorbs one of the polarizations.  They are oriented so that the more strongly reflected polarization will be absorbed by the polarizer.  You can see this by looking at reflections from water, pavement, or car windshields.  If you rotate the glasses, you will see the reflection decrease in the normal wearing orientation and increase when the glasses are rotated 90 degrees.\n\nThe plastic polarizers in sunglasses are made by starting with a thin film of polyvinvyl alcohol (PVA) that is stretched to align the molecules.  The film is then treated in an iodine solution. The iodine molecules are incorporated into the PVA film and aligned with the oiented PVA molecules.  The iodine treated film is then coated with a clear protective plastic layer to protect it from humidity which would ohterwise bleach the iodine from the film. Light that has its electric field polarized along the direction of the iodine chains is absorbed.  Light that is polarized perpendicular to the chains is transmitted.
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Without going into the complexities of molecular theory, things APPEAR black because they absorb many wavelengths of visible light/EM radiation including infrared (heat) thus making them hotter.  Because everything is absorbed, no light is reflected and you see no light or darkness/black.  The excess absorbed energy manifests itself in many ways such as adding to the vibration of the molecules or heat.\n\nWITH slightly more detailed quantum theory:\n\nThe energy is absorbed by the electrons of the atoms that make up the black material and excite them from a ground level to a higher level or energy state.   From quantum mechanics, we know that these electrons will only absorb light of a given frequency/energy - that which corresponds to just enough energy to go from level 1 to level 2 to level 3 and so on - and will not absorb other frequencies (hence why we have red - green & blue absorption, etc).  In these black materials it just happens that the differences between all the energy states correspond to most frequencies of visible light giving you dark/black colours or full absorption.  At higher energy states, the atoms and molecules have extra energy which allows them to vibrate more or become hotter.  They're also less stable and reemit this energy in the form of infrared (heat) to get back to the more stable low energy state.
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1) Generally, rays of the sun which is called radiation lay between 400 nm (nano meter) to 700 nm.\n2) Below 400 nm is called ultra-violet and above 700 nm is called Infra-red.\n3) Both are invisible to the human naked eye.\n4)Infrared radiation is used to obtain pictures of distant objects and the detection of infrared radiation is used by astronomers to observe stars and nebulae.
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Yes. those of frequency higher than infra red are absorbed by the PV. IR travels right through the silicon in the PV
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As a source of infrared radiation, most modern FTIR devices use a heated ceramic element.  This usually consists of a coiled wire heater that has been coated with ceramic.
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The type of plastic selected has a great influence on the performance of the plated plastic part. ABS plastics are the base materials in most cases.\n\nCheck out the following:
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some is reflected by the glass, and some passes straight through.  A tiny part will go towards heating up the glass itself, as it is absorbed during its transition throught the glass.
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I do not know how deep you want to go. This could get quite complicated. \n\nThe simple answer is that it absorbs infrared radiation. That is, it is opague to IR light (heat). \n\n\nHere is how it does it:\n\nLight at all wavelengths falls on the atmosphere. Some gets transmitted to the ground. The surface absorbs this radiation, and some of it gets reradiated as heat, or IR light. The carbon dioxide in the air will not let it escape out into space.\n\nOf course, one can make this far more sophisticated and detailed.\n\n- - - - - - - -  - - - - \n\nObviously this is a multiple-choice homework problem. I am afraid if you cannot figure out which answer to choose from my response, then you have some problems. You need to ask the teacher for help. I will not spoon-feed you.
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Metal is an excellent conductor of heat while plastic is not.
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Dark animal fur. Black surfaces are both good absorbers and good emitters of infra-red radiation.
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I can think of two ways to measure the absorption and reflection coefficient of a material.  The first would only work with a polished surface.  First measure the intensity of a laser beam with a photodetector, then shoot the laser beam at the surface and aim the reflection at a photodetector.  Coefficient of reflection = transmitted intensity/initial intensity  (coefficient of absorption =1-reflection).  The other, harder way, which would work with any material, is to measure the heat gain in the target.\n\nFor this you're gonna want as small a piece of the target material you can get so that the laser still completely hits it.  Now attach a thermistor to the back of the target (again the smaller and thinner the target the better, ideal would be a foil just thick enough to be completely opaque).  Now shoot the laser at the target and measure the temperature as a function of time  It should be linear up until it starts radiating nearly as fast as it absorbs energy, so take points until it starts to level off and drop points after that.  Now find the specific heat of the thermistor-target apparatus by dipping it in water with a thermometer in it, using the initial and final temperature of the water, the volume of the water, and the initial temp of the apparatus, determine the heat it absorbed per degree it's temperature changed (this will actually give you specific heat*mass which is fine).  Now convert your temperature vs. time data to heat vs. time using the specific heat you determined (temp*(specific heat*mass)).  The slope of the line of best fit for this data will give you the rate it absorbed energy in watts.  Divide this by the lasers output in watts and you get the absorption coefficient.
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Check this link... Has good info...:\n\nhttp://en.wikipedia.org/wiki/Plastic
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As mechanical engineer this is out of my normal field but felt you deserved an answer of some sort.\n\n"Because of diffraction effects caused by slits or apertures in optical measurement systems, the radiation energy which is directed towards a particular region on a sample will be spread over a larger area than desirable. By employing an apodizing filter in the radiation path in such system, diffraction tails of the system will be reduced. The apodizing filter preferably has a pattern of alternating high transmittance areas and substantially opaque areas where the locally averaged transmittance function is an apodizing function. In the preferred embodiment, the locally averaged transmittance function varies smoothly and monotonically from the periphery to the center of the filter"\n\nI see the theory here, also found on on using an apodizing mirror to stabalise images in a telescope\n\n"I built and used an apodizing screen for my 6" f/8 scope many years \nago. I made it by layering several layers of window screen, each one \nwith a circular cutout of different diameter. The result was an aperture \nmask with a step-wise approximation to a smooth apodizing function. It \nwas claimed to improve contrast for planetary viewing. Anyway, my \nexperience was that it seemed to make the image more stable but if it \nimproved contrast, I couldn't see it. If you do this on-axis, the \ndownside is that your diagonal mirror will now become more of a factor \nin the contrast equation. The bottom line is I wouldn't recommend it."\n\nAlso "An excellent reference for all sorts of technical techniques is\n>"Procedures in Experimental Physics" (also printed under the title\n>"Physical Laboratory Practice") by John Strong.  I don't recall the\n>publisher, but it came out in the 30's.  The bad news it that it's been\n>out of print for decades (and some SOB stole the copy I got from my\n>father!); the good news is that an outfit called Lindsay is reprinting it\n>in paperback.  (Don't have their name/address here in the office; I'll try\n>to remember to look it up tonight.)\n>\n>                            Dr. Kurt Hillig\n\nEvery ATM should have a copy of this great book. Lots of stuff on\nmirror making, figuring, special laps,making flats, prism ,etc.\nThere is nice modifed Draper machine ( upper disk also powered)\nand a homemade diamond cutting wheel to cut small glass blocks.\n( I would like to build this one someday ) A great section on\nkinematical mechanical construction. Yeah this a mid 30,s book but the \ninfo\nstill can be used. No I don't work for Lindsay Publications,<G>\n\nBob Pfaff\n\n\n This book, in paperback form, can be ordered from\n      http://www.amazon.com, on the Web. It can also be ordered\n      through your local bookstore. Amazon prices it at $23.95, and\n      provides the following information:\n\n      Published by Lindsey Publications\n      Publication date: June 1986\n      ISBN: 0917914562"\n\nSorry couldn't find any really decent expplanations, but at least you've got a starting point.
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Their behaviour when you heat them:\nThermoplastics soften, and re-set on cooling.\nThermosetting plastics don't soften at all, and merely catch fire if you overdo the heating!
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UV carries more energy than infrared. UV has the highest frequency. \nUV is not the cause for globalwarming. As the atmosphere gets more and more CO2 it will trap more infrared light coming from earth. CO2 is the cause for globl warming. \nThe infrared radiation from earth is the radiation it emitts as the surface absorbs light from all other frequencies, including UV, although not alot of UV reaches the surface. Instead it is absorbed by the ozonelayer. That means it gets hot up there but that heat (or infrared light) doesn´t make it down to the surface. Instead it is radiated off into space.