Absorption Definition and 534 Threads

Hi! In my lab class, we are using a photomultiplier to examine gamma ray emission lines and determine absorption coefficients of different radioactive materials. Homework Statement As we test for absorption (by layering on metals, incrementally increasing the thickness), we consider spectral...

A note from Newton's Principles definition #4 in 1687: Impressed Force - This force conflicts in the action only; and remains no longer in the body when the action is over. In Einstein's second paper on relativity in 1905, he explicitly concludes: "Radiation carries inertia between...

I recently learned that a free electron can't absorb a photon and derived it by showing it would be impossible to conserve both momentum and energy if that were the case. It seems like the same argument would extend to other fundamental particles. Is it true that no free fundamental particle can...

In an indirect absorption process that an electron jumps from the top of the valence band to the bottom of the conduction band,why a phonon must be involved to conserve the momentum? At these two points (top of the valence band and bottom of the conduction band) the electron momentum is zero so...

Hi all, I am looking for the best material for IR (infra red) absorption, preferably something that I can make it into a thin film; any material that would work from semiconductors, metals to more exotic materials like graphene or... I appreciate your help. Thank you

I am working on an automotive project and am looking to pick up any gains that I can. In doing so, I've been studying the effect that colour has on thermodynamic characteristics. To be specific, I am interested in finding: A) What colour(s) will help retain the most heat i.e. minimize thermal...

In the paper H.B. Callen, T.A. Welton, "Irreversibility and Generalized Noise", Phys. Rev. 83, 34, (1951) the authors arrive at an interesting formula for average power continually absorbed by a quantum system ( = with discrete states of definite energy) under action of a harmonic...

I need to characterize some colloids (extract the concentration of material inside). Why should I dilute the sample before measuring it with spectrometer?

The absorption spectra of some materials appear as the absorption bands (for example: TiO2 powder) while the other appear as the absorption peaks (for example: Quantum dots). Please explain why they are different?

On PF, to answer why atmosphere is transparent, users explained that atmospheric gases such as oxygen do not have absorption lines in the visible spectrum. On UColorado website, under Spectral Lines, they show that Oxygen has many visible lines in its spectral signature. This confuses me...

Hi I'm trying to follow a derivation, I don't think I'm allowed to post the content (copyright) but the paper is here: http://www.sciencedirect.com/science/article/pii/002240739290117M. Does anyone have access to this and know a little bit about integrating over solid angles? I've spend half...

Homework Statement A hydrogen electron is at its ground level when it's radiated in wave length of 94.92 nm. As a result it arrises to level a. then emission occures with frequency of 2.34*10^14 Hz and the electron falls to level b. What's the energy difference between the 2 levelsHomework...

Hi guys, So my project partner and I are struggling to solve a problem with our laser spectroscopy data for rubidium isotopes and I thought it may be a good idea to see if you could help us. If you take a look at the attached image you will see that the blue line shows our doppler free...

The Hpyerphysics site, while discussing coherent light of lasers, says that… “the emitted photons are "in step" and have a definite phase relation to each other.” So now I wonder about electrons of an atom absorbing photons. Assuming the correct energy level for a given photon, is the...

When we shine light on an atom, it can absorbs this radiation, stimulating its electrons to jump to a more energetic energy level. This lasts too little time, and when the electrons come back to their original (fundamental) energy level, they emit the same energy they had absorbed before. This...

Well, this question may seem elementary to you but I simply do not have a background for it. Now the question: Sun radiation resembles a blackbody at over 5000°K. A solar cell's temperature is around 300°K. If we neglect loss in the cell, its emission and absorption coefficient are equal...

Homework Statement Could someone please help me with this question? A single-celled organism contains N particles, some of which are of type A, the others of type B . The cell is said to be in state i , where 0<=i<=N if it contains exactly i particles of type A. Daughter cells are formed...

Could someone please help me with this question? A single-celled organism contains N particles, some of which are of type A, the others of type B . The cell is said to be in state i where 0<=i<=N if it contains exactly i particles of type A. Daughter cells are formed by cell division, but...

Homework Statement Given the carrier concentrations (1.4x10^16, 3.2x10^16 and 5.3x10^16 /cm^3), verify that the free carrier losses scale linearly. (use λ=10μm) Homework Equations Those concentrations are given by this paper: A. Chandola, R. Pino, and P. S. Dutta, "Below bandgap optical...

Hey all, Does anyone know of a paper or experiment that verified that a single photon is absorbed in exchange for electron excitation? Thanks

Hi all, I'm relatively new to the forum, but excited to be a part of a community discussing physics, as I lack company to really discuss my research at my place of work (university), as I am a physicist working solely amongst chemical engineers. I am using a UV-Vis spectrometer, with the...

can anyone give an example in which a nucleus absorbs a neutron and becomes a stable nucleus? or the combination must break into parts?

An aqueous solution of yeast nucleic acid of length 2.0*10^-2m and concerntrated 2.0mol m-3 has an absorptivity of 25m2 mol-1 at a certain wavelenght. calculate the percentages tranmission at this wavelenght. this is an example that i don't understant, please help me to simplify it and...

I am trying to understand radiative transport of thermal energy in materials from first (or close to first) principles. I do not understand the systematics/statistics of how photons are emitted and absorbed in a medium. How is it that photons can be emitted at so many wavelengths and atoms can...

Hello Forum, how is is possible for quantum dots to offer a wide, broadband absorption spectrum but still have a single distinct emission wavelength? How is that asymmetry possible? For example, I would think that if we can absorb, say, 4 wavelengths, we can also emit those say 4...

Homework Statement The fluorescence spectrum of anthracene vapor in the figure shows peaks with maxima at 440 nm, 410 nm, 390 nm, and 370 nm, whereas the absorption spectrum has peaks at 360 nm, 345 nm, 330 nm, and 305 nm. Assuming that only one vibrational mode contributes to these...

This is an observational exercise where I have to find several different light sources and observe their spectra through a diffraction grating, then record my observations. I need two sources of each (i.e. continuous, emission, absorption). Continuous and emission are fairly easy, but for the...

Hi All, I am currently investigating a method of absorbing heat from radiation. This is being done to harness heat from skin. I was wondering what was the best method to do this? Is there a particular material that is best suited to do this? I know that having the emissivity value of the...

Homework Statement If a round trip gain in a 56.8 cm long laser is 5.16%, what is the net gain coefficient (g-\alpha). g is the small signal gain coefficient \alpha is the absorption coefficient L-length of cavity Homework Equations The Round Trip Power Gain: Gr= R1*R2*...

Homework Statement My class is currently going over electronic energy levels, and the book states that an electron with a kinetic energy of 9.8eV could excited two mercury atoms (first excited state above the ground state of mercury is 4.9) to their first state above the ground state...

Hi, does anyone know how to calculate the total absorptin of a sample from its labdam-absorbance spectrum? I found a paper where the author find it as the average of the data, another one numerically integrate the spectrum over the whole lambda range.. but the two methods give different...

I am solving a temperature distribution problem related to laser drilling. In the equation I am encountering a term called ' Absorption or extinction coeffcient' of alumina. Can anybody tell how to find this ?

Hi When talking about atoms absorbing a photon, a classical picture is utilized. The intuitive picture often presented is that when an atom absorbs a photon, a recoil of \hbar k is obtained by the atom. After a time \tau=1/\Gamma the atom emits the photon again. So the force in this picture is...

How much mass would even the smallest of black holes have to absorb (keeping also in mind the radiation lost as it grows) to obtain its size? And considering the largest Black holes discovered so far, how much mass would it have had to gobble up to get to that size? On the average, how much...

'Ello, I have a question regarding the results in this paper (and another which I will mention later) http://arxiv.org/abs/hep-ph/0212199 Now, I'm not so concerned about the 'braney' bit, but more their definition of the cross section in Eqn. (46). They have included the usual (2j+1)...

Hello, I am trying to determine the band gap of an amorphous material (a glass sample) and I read that you can do this from the determination of the optical absorption edge. From this kind of measurements you fitt an equation of the type (αhν) = B (hv-Eo) 2. my question are: 1 - is it...

Hi everyone. I was wondering how badly aluminum affects RFID waves (860-960MHz)? Do they completely absorb, reflect, combination of the two? I'm having issues with my testing of RFID. I'm getting some dead zones and I think it could be because of the portal frame the antennas are mounted on...

Hi all I was reading through an astrophysics book{1} and there I came across this sentence: " A dust cloud can either scatter or absorb light that passes through it. Since shorter wavelengths are affected more significantly than longer ones, a star lying behind the cloud appears reddened...

I am trying to understand why radio waves are not greatly attenuated by the atmosphere due to scattering or absorption? I have tried searching the internet and can't find any satisfactory answers. Please help. Oh and does this property somehow relate to why they are used to transmit information...

Emission of light from a solid object From my textbook (explaining why an apple is red): We imagine that the red apple in the picture is illuminated by daylight, IE light which contains all the wavelengths of the visible spectrum. The apple is red because the main part of the light it...

Been viewing this site for a while now and very much appreciate all the contributors! I can't seem to find an answer to this anywhere so I think I may be misunderstanding the basic ideas of absorption and emission spectra... An absorption spectrum, say of our Sun, is as I understand it the...

When an element is excited by some method, it emits electromagnetic radiations of definite wavelengths. The arrangement of these wavelengths in order of increasing wavelength is called emission spectrum of the element. (as per my book) But, the definition of absorption spectrum, I don't...

When a ray interacts with a solid if the surface is polished reflection occurs. This is true even if the material absorbs at the specific wave lenght? In other words if the material absorbs at the specific λ, can occurs Fresnel reflection ? Or: Fresnel reflection has always all the same λs of...

I am building an enclosure for my laser that emits at 1550nm. I need to integrate a window for the laser light to pass through. Anybody have any recommendations on what kind of glass would work best so that the optical losses are kept at a minimum? Ideally, it would be commercially available...

I'm working on an experiment to measure the quenching of an oxygen-sensitive dye. The excitation light is blue and the light fluoresced is red. When I collect data, there is always a peak for blue and red, which makes it impossible to measure really the quenching in low dye concentrations...

I have had a question that I cannot get an answer for. I recently had an exam for energy in the nucleus which included a question about why lead nuclei would be inadequate for use as a moderator in a reactor. When I got the answer for the question, it stated that the lead nuclei reflect neutrons...

Ok thanks for the responses to my other question; I think I now have it. I have a follow up question – that is almost on the same topic (but not quite) The complete spectrum (arund 200nm to 380nm) of UV light is absorbed by some plastics?? Elections will be moved to a more energetic orbital...

Colours of objects produced by light due to reflection & absorption! Hi fellow members! We know that colours of our surrounding things is due to the absorption & reflection of particular wavelength of light. But we also see same colours of objects in bulb light aur tube light. Do they also...

I am currently trying to graph the absorption coefficient of Copper tetra-tert butyl phthlocyanine. I have the extinction coefficient vs wavelength graph and refraction vs wavelength graph however I don't know how to use these to graph absorption coefficient. E(eV)=1242.4/λ absorption...

we know that the quantum well absorption coefficient is calculated by summing over the electron-heavy hole and electron-light hole transitions: α_{w}(E) = \sum_{n}α_{e_{n}-hh_{n}}(E) + \sum_{n}α_{e_{n}-lh_{n}}(E) where n is the n^{th} transistion. but when the photon flux is incident...