# What is Absorption coefficient: Definition and 22 Discussions

For "attenuation coefficient" as it applies to electromagnetic theory and telecommunications see Attenuation constant. For the "mass attenuation coefficient", see Mass attenuation coefficient.The linear attenuation coefficient, attenuation coefficient, or narrow-beam attenuation coefficient characterizes how easily a volume of material can be penetrated by a beam of light, sound, particles, or other energy or matter. A large attenuation coefficient means that the beam is quickly "attenuated" (weakened) as it passes through the medium, and a small attenuation coefficient means that the medium is relatively transparent to the beam. The SI unit of attenuation coefficient is the reciprocal metre (m−1). Extinction coefficient is an old term for this quantity but is still used in meteorology and climatology. Most commonly, the quantity measures the value of downward e-folding distance of the original intensity as the energy of the intensity passes through a unit (e.g. one meter) thickness of material, so that an attenuation coefficient of 1 m−1 means that after passing through 1 metre, the radiation will be reduced by a factor of e, and for material with a coefficient of 2 m−1, it will be reduced twice by e, or e2. Other measures may use a different factor than e, such as the decadic attenuation coefficient below. The broad-beam attenuation coefficient counts forward-scattered radiation as transmitted rather than attenuated, and is more applicable to radiation shielding.

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1. ### Absorption coefficient and Linear Optical Susceptibility

##\alpha## is considered to be the absorption coefficient for a beam of light of maximum intensity ##I_0##. It's related to the complex part of the refractive index as we have shown above. Now, I have a doubt. Should I solve for ##k## from the quadratic equation in terms of the linear optical...
2. ### Why Do Different Materials Use Different Units for the Absorption Coefficient?

Why is the absorption coefficient (##\alpha##) of water is always given using the units ##\text{length}^{-1}##, while for other materials it is often given by ##\text{length}^{2}.\text{mass}^{-1}##? For instance, this paper uses ##cm^{-1}## for water and yet ##cm^2 / \mu g## for other...
3. ### Negative absorption coefficient in muon absorption?

Homework Statement I am conducting an experiment where I am interested in finding the absorption coefficient of different materials as muons pass through them. My data was all well until I realized more muons were measured AFTER they passed through one of the materials, which makes no sense...
4. ### I Difference between absorption and scattering cross sections

Hi. I'm trying to model the attenuation (extinction) of a weak laser through a gas sample using the Beer-Lambert law. I've found that the attenuation cross section can be written as the sum of both a scattering and absorption cross section, however I'm having difficulty finding a source that...
5. ### A Relation between the absorption coefficient and the transmittance spectrum

hi every one can you tell me how to calculate the absorption coefficient of a thin film using the absorption and the transmittance spectrum plotted as a function of the wavelength (knowing that i don't know the thickness of the film )
6. ### I Calculation of the absorption coefficient for GaAs

Anyone can explain me this example? I substitute value for e = 1.602*10-19; m0 = 9.1*10-31; pi = 3.14; and calculated value for μav in matlab. I received 1.7104*10-19. But in exam this value is 0.68*10-25. What is i wrong? please help me. Thank you.
7. ### How to calculate required concentration of absorbing agent

Hi All, I am designing an optical solid phantom to represent tissue optical properties (scattering and absorption coefficients). I know what should be the optical properties of tissue but I don't how much absorbing agent should I add to the mixture so that the phantom exhibit my desired...
8. ### Negative absorption coefficient

The fact that energy in a laser can propagate without much loss over long distances is quite shocking ! It's a renowned fact that energy is dissipated when propagation takes place through any medium... (I'm fully aware that laser is an exception) But I have quite a difficult time understanding...
9. ### Convert absorption coefficient units between Hitran, Lifbase

Hi, I have some modelling code that uses data from Hitran 2012 (https://www.cfa.harvard.edu/hitran/Download/HITRAN2012.pdf). I want to use some data from Lifbase but unfortunately the absorption coefficient units do not match. Lifbase units are given in m3 J-1 s-2 whereas Hitran units are...
10. ### What is the absorption coefficient of black-colored water?

I saw this on Wikipedia http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water Isnt it supposed to less than 1 ? maybe it has something to do with the unit ..why is it in m^-1?
11. ### Absorption coefficient of aluminium for microwaves

I am looking for an exact value of absorption coefficient of aluminium for microwaves, but I can not find it in the internet. Anyone knows where I can find it?
12. ### Calculating Absorption Coefficient

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...
13. ### Absorption coefficient of quantum well

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...
14. ### Molar absorption coefficient of Catechol

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.
15. ### Mass absorption coefficient of aluminium

I was conducting an experiment, and we had to use a radioactive source and a Geigor counter, in conjunction with aluminium plates. Using the data we produced we had to graph an absorption curve and obtain a value for the mass absorption coefficient of aluminium. Then we had to compare this...
16. ### Help on Sound Absorption Coefficient Calculation

Hello all, I come from musical sciences, but I'm trying to learn something about acoustics, so here I am, asking for some help about the impedance tube sound absorption coefficient test. I have and impedance tube, two microphones technique (ISO 10534-2), B&K microphones connected to the...
17. ### Calculating the absorption coefficient from little information

Hello, I am currently creating a program that calculates the change in observed intensity (nadir) from initial intensity within the atmosphere. As I am studying particular compounds, a first suggestion for my work is to produce a 'forward model' based on very simplistic radiative transfer...
18. ### Absorption coefficient per unit path length determined for excitation

How is the absorption coefficient per unit path length determined for excitation sites in a host crystal with an excitation site density of N and a bandgap of the excitation site equal to the photon energy? What I am trying to determine is how many photons will be absorbed for a given length.
19. ### Why is the mass absorption coefficient used rather than the linear absorption?

Homework Statement Why is the mass absorption coefficient used rather than the linear absorption coefficient? Homework Equations mac=lac/density The Attempt at a Solution is it because mac is independent of physical from?
20. ### To calculate absorption coefficient

want to calculate absorption coefficient or absorption crosssection for 1% C2H2 gas Path length = 1meter Absorbene = 0.32 concentration = 8500ppm pressure = 1 atm Temperature = 25C I need to express this concentration to mol/cm3. Pls let me know if u have anyidea
21. ### Two photon absorption coefficient of silicon

Hi, is there a way to calculate the two-photon absorption coefficient of silicon? I am especially interested in the two-photon absorption coefficient of silicon for the wavelengths 1030nm, 515nm and 343nm. Thanks for any help!
22. ### Absorption Coefficient of Aluminium

Hi. I am new here! I'm doing a experiment on the absorption of beta radiation of aluminium and I need help! :redface: Does anyone know what the absorption coefficient of aluminium? Or at least where I can find it. Thanks in advance! o:) P.S. Sorry if I've posted in the wrong part of the forum...