Absorption Definition and 495 Threads

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...

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...

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...

Hello , I was trying to calculate the effective absorption cross section ( group constant) of U-238 in the resonance region between neutron energies (1 ev - 10 kev) but as you can see from the picture U-238 has a lot of resonance at this region, I was wondering if there is a way I can obtain...

Yo does anyone have a table from like Brookhaven or somewhere of absorption cross sections for just about anything in the 1/v region? And have the precision included in the data. I'm doing a pretty quick statistics assignment.

When scientists analyze proteins (chains of amino acids), often times light spectroscopy is used. Light is passes through a cuvet containing dissolved protein, and the absorption is measured. My question is: How do bonds absorb energy? What is the actual mechanism? I have been told that the...

say we have integers 0-10. We start with N and the probability that N grows by 1 is .69. The probability that N decreases by 1 is .31. Thus obtaining N+1 after one time step is .69 and similar obtaining N-1 is .31. Once N reaches 0 or 10 it is absorbed and can't move from there. My question is...

Homework Statement Prove the second absorption law from Table 1 by showing that if A and B are sets, then A ∩ (A ∪ B) = A. Homework Equations Absorption laws A ∪ (A ∩ B) = A A ∩ (A ∪ B) = A The Attempt at a Solution i will show A ∩ (A ∪ B) is a subset of A x is any element in A...

Hi everyone Homework Statement I'm looking for the molar absorption coefficient of Catechol but I can't find it anywhere. Can anyone help me out? I searched the internet as well as some books we have in our library, but I wasn't able to find it. Thanks for you help.

Are there sky surveys that perform gamma-ray absorption spectroscopy? I was wondering if dark matter might absorb gamma radiation. I have done a simple Bohr-atom type calculation assuming a dark matter model of a bound state of a North and South magnetic monopole and found a Rydberg energy...

The nutrition label on a package of processed cheese food indicates that a 20.0 g serving has 175 Calories. To test this you put a small piece of cheese under a can with 100.0 mL of water and burn the cheese. You find that 1.0 grams of cheese was burned to heat the water. Assume that all of the...

Homework Statement The atomic site that is in thermal and diffusive equilibrium with a gas of Helium atoms that is on the surface of a metal can either absorb an atom of Helium or it can be vacant. (a) What is the Grand Partition function of the system? (b) Derive the average thermal...

Hello Forum, when a wavefield is incident of an atom and the photon have the right energy (equal to the band gap energy), the photon is absorbed and disappear... But isn't the photon re-emitted later on and allowed to propagate through the material or does all its energy get lost into heat...

Homework Statement At what rate is a refrigerator absorbing heat if 2·15 kg of water at 21·5 °C is just frozen in 2·00 h? Homework Equations Q = mL Q = mcΔT The Attempt at a Solution Rate of Heat Absorbed = Q/t = mcΔT/t = (2.15*4.2*21.5)/(2*60*60)...

Hi everybody. I'm new here and, first of all, sorry for my bad english :-D I'm studying photoelectric absorption in semiconductors. The book (and professor too) says that, in the conservation law: ki + kph = kf (where ki and kf are wave vectors of initial and final electron state, and...

I'm looking for information about absorption of light per unit (atom, molecule, stoichiometric) in a liquid vs solid. For instance, imagine a unit cube filled with a saturated solution of, say, potassium permanganate, and shine a laser beam through it from bottom to top and measure the...

Homework Statement In an experiment carried out with a beam of thermal neutrons it is found that on traversing a 2mm thick foil of 197Au, some 70% of the neutrons are removed. What is the total thermal neutron cross-section for this isotope of gold? (Density of gold: 19300 kg m-3) Homework...

Dear PF, I'm a graduate student working in an ultracold atomic phys lab. We're trying to build a new machine with Li6 as one of the components, but in order to cool it we need to do saturation absorption spectroscopy on a separate stand-alone cell in order to tell our lasers what frequencies...