can we detect the composition of a material , by focussing a radiation and studying the reflected signal?
436829
What you are asking about is in the realm of surface science.  There are many analytical techniques and I will not try to go through all of them.  This is a good starting place: http://www.uksaf.org/tech/list.html
420181
no and yes,\nyou cannot "see" it with a big microscope and your eyes since the wavelength of light is larger than an atom. \n\nBUT using a beam of electrons, which have wavelengths smaller than an atom, you can use equipment that can detect the reflected electrons. this is the concept behind an electron microscope, like the previous poster talks about.\nhttp://en.wikipedia.org/wiki/Electron_microscope
752209
An OTDR works by firing light down a fibre optic cable and then measuring the levels of reflected light and knowing the time it takes for the reflected light to be sensed it can tell how far the point of reflection is. They operate in a very similar fashion to radar and are designed to pick up faults in fibre optic cables, be they joints/splices, pressure faults, or clean breaks as these will all reflect light back down the fibre. The principles are also the same for radar in that the shorter the pulse the better the discrimination and the more accurate the outcome. In some case in fibre fault finding the operators of the OTDR will introduce faults on the fibre by submersing it in liquid nitrogen and then using it as a reference point to find the true fault. Having worked in fields where its not easy to find a fault with excavating kilometres of earth the nitrogen method is a god send if somewhat damaging to the cable.
632126
detection of metal compounds and their concentration, as opposed to other types of spectroscopy which deal with organic, or carbon based compounds.
558537
Good question.  The reflectivity of a surface is very sensistive to a film and with specialized equipment, submonolayers can be detected.  I knew somebody that was studying thin films of water on silver and she said she noticed a difference.  I think that was about 10-100 monolayers that she was working with.  My guess is about 50 nanometers.
340206
The scanner sends out a laser beam that reflects against the barcode on the object. The scanner is programmed to recognize the reflections of barcodes and use those to identify the product.
522524
The light is reflected
488134
It measures mineral hardness.
748559
The dielectric constant of a material can be found by a variety of static electrical measurements. The complex permittivity is evaluated over a wide range of frequencies by using different variants of dielectric spectroscopy, covering nearly 21 orders of magnitude from 10−6 to 1015 Hz. Also, by using cryostats and ovens, the dielectric properties of a medium can be characterized over an array of temperatures. In order to study systems for such diverse exciting fields, a number of measurement setups are used, each adequate for a special frequency range.\n\n    * Low-frequency time domain measurements (10−6−103 Hz)\n    * Low-frequency frequency domain measurements (10−5−106 Hz)\n    * Reflective coaxial methods (106−1010 Hz)\n    * Transmission coaxial method (108−1011 Hz)\n    * Quasi-optical methods (109−1010 Hz)\n    * Fourier-transform methods (1011−1015 Hz)
578383
There are two types of substances\n1] Transparent.eg.Glass   2] Opaque.eg.iron                    Glass allows light to pass thru it as atoms in glass are in contact with each other.So when 1 atom receives energy,it vibrates with a greater amplitude[atoms are always in a state of vibration].It disturbs the neighbouring atom which accepts the energy liberated by the 1st atom.It transmits the energy to the next atom and so on....\n\nIn case of iron ,atoms areplaced even more closer which results in reflection of the entire light.In case of glass,there is partial reflection and partial refraction
854178
Uh, I'm not smart on this, so I'm guessing here, but...\nSince different frequencies and wavelengths are what determines what color is being reflected, there has to be some way to quantify the amount of each in different hues of different colors.  Does that even make sense?  I don't know...
473990
A non-invasive analytical technique with an infinitely broad range of applications in plant biotechnology and food processing. It is similar to MRI (Magnetic Resonance Imaging) in that it can be used for medical applications. Non-destructive analysis with this tool can be applied to a wide range of research challenges, including the determination of chemical structure, microimaging and plant metabolism studies.\npbi-ibp.nrc-cnrc.gc.ca/en/media/glossary.htm\n\nAn analytical technique devoted to the identification of the elements and the elucidation of atomic and molecular structure by measurement of the radiant energy absorbed or emitted by a substance in any of the wavelengths of the electromagnetic spectrum in response to excitation by an external energy source.\nwww.fire.org.uk/glossary.htm
266423
The essential answer to your question is YES - the absorption coefficient of a material reflects how well it absorbs acoustic energy.  This is another way of measuring the FREQUENCY RESPONSE of a material.\n\nAbsorption coefficients generally are qualified with a "typical operating range," that is, a range of frequencies over which the absorption coefficient is essentially correct (within, say, +/- 5% error - any good listing of absorption coefficients will list the accompanying error).\n\nFor most typical materials, the AAC is generally constant through the human auditory spectrum.  One notable exception to this is water - high frequencies are halted in water after only a few meters, but low frequencies (i.e., whale songs) can be transmitted over 10,000 miles away.
878247
Simply put, you can look at light or matter as waves or particles, depending on the experiment performed.
608906
may be with internal reflection
192375
I would suggest trying methods where you do have a hole to confirm results.  For example, light is reflected (and refracted?) at every surface and thickness of a transparent media where there is a change in density or crystal structure.  You may be able to shine a light (at night or under a blanket?) to detect the bottom of the ice and compensate for refraction where the actual thickness may differ from apparent thickness.  Use a ladder to spread your weight if the strength of the ice may be marginal.  Would a laser pointer work better than a flashlight?  Good luck.
364018
Ultrasonics appears to be a possible way. You can also check on www  GlobalSpec.com  , lots of stuff there.\nI forgot ! Eddy-current testing has been used for many years in non-destructive testing of non-ferrous metals.A probe with an alternating current of a frequency decided by the skin-depth of penetration can be used to measure impedance change near a crack etc. Alternately a dc current could be applied via a probe and possibly use a Hall plate sensor to detect field distortions. The subject is very interesting and there is much relevant work to be done.\nNow in the case of non-metallic materials, we can consider a capacitance measuring device; there must have been work done on this method.