Questions tagged [absorption]

A transition by which the energy of at least one photon is completely transferred to a material.

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Why the extraterrestrial solar spectrum is higher than blackbody spectrum? [duplicate]

I am reading "Radiation Heat Transfer by Michael F. Modest(2003)" and the author talks about how the solar spectrum can be approximated by black body radiation at 5777K. I'm finding the plot ...
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Energy of exciton formation in semiconductors

Many sources I've seen have alluded to: An exciton can form when a material absorbs a photon of higher energy than its bandgap I looked at absorption enhancing effects of excitons, and am aware of ...
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What variables affect an object's absorption of invisible light?

Say I have two objects (we'll call them object $1$ and object $2$) of the same material but of a different colour, placed at the same distance away from another object (we'll call object $3$) that ...
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Balmer series for ionized lithium

I am trying to calculate the wavelength for the first spectral line in a Balmer-series for a two times ionized lithium, $\text{Li}^{2+}$. I know that the atomic number $z$ is 3 for lithium and it is ...
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Excitons - Increase in absorption

I have consulted a book by Mark Fox on Optical Properties of Solids, and it states: " The absorption of a photon by an inter-band transition in a semiconductor or insulator creates an electron in ...
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Where does this formula of absorption cross section come from?

My professor gave us a formula for absorption cross section, but he said he did not remember where he found it. The formula is given by $$\sigma_a =\frac {1} {|\mathbf E_i|^2} \int_V k \epsilon^{''}_r ...
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What is the reason for the appearance of absorption lines in the spectrum of light coming from the sun?

If your answer was that the sun's atmosphere absorbs some photons, I don't think so. Because the atom, after absorbing a photon, it seeks stability and emits an electron in a short time compared to ...
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Can a photon's angular momentum couple to an electron spin, to cause a spin-flip (thus allowing intersystem crossings)?

Been reading up on intersystem crossing and have gotten rather confused by: a photon possesses an angular momentum of $h/2\pi$ so it can couple to an electron spin and in principle induce any ...
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Problem regarding the absorption spectrum of the sun

Some of the wavelengths of light that are emitted from the sun will be absorbed by atoms in the outer layer of the sun and also the atmosphere of the sun, and we see this as absorption lines in the ...
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Determine molar extinction coefficient from data set

How can you determine molar extinction coefficient from the graph of Transmittance vs Wavelength, where the solution concentration and thickness of cuvette are known and constant by using Beer-Lambert ...
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Why do atoms absorb photons at specific wavelengths and reflect photons at wavelengths other than the absorbed photons?

As we already know that the electron emits light photons when it travels from one orbit to another, and that causes this transition is the electron absorption of the incoming photon. But when the ...
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Does absorption in the cladding material change the real value of the propagation constant of a waveguide?

Imagine two scenarios: two cladding materials with the same real refractive index, but one has absorption while the other does not. Now, these materials act as the top cladding of a waveguide (for ...
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IR and UV transmissivity window of the (human) eye

Given this image: I just assume that the eye is made out of glass, so I wonder how is it that IR and UV radiation is absorbed by it? I would understand one of them but why is it transmissible for ...
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What determines if a photon is absorbed or not, i.e. if an object looks black or coloured?

What is it that make some material look black? What I mean is, why do some atoms absorb photons while others transmit them? (Correct me if I'm wrong but I think all photons are absorbed by an electron,...
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What effect does surface have on light absorption at different wavelengths?

I am a bit confused and need a well rounded explanation. Have a look at two scenarios: A metal plate with small scratches on it appears diffuse in the optical spectrum, because the roughness reflects ...
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Ultra-violet optical transitions for $\rm ZnO$?

Is there any paper discussing the d(GAMMA3)-GAMMA1 optical transitions at around 7 eV for $\rm ZnO$ (W)? Will the negative effective mass/saddle point makes it a 2D (M1) transitions?
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Reconciling two descriptions of fluorescence

I am currently studying the textbook Infrared and Raman Spectroscopy: Principles and Spectral Interpretation, second edition, by Peter J. Larkin. Section 9. Selecting the Raman Excitation Wavelength, ...
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How much hotter will an object get if I paint it black?

I have read these threads If black is the best absorber and radiator, why does it get hot? Black and white matters. But why and how? If a black body is a perfect absorber, why does it emit anything? ...
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If black is the best absorber and radiator, why does it get hot?

I can guess that it’s emission peaks at a higher temperature than white. So when a light is turned onto a black and white piece of paper, the initial condition is not at equilibrium. As black absorbs ...
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When does an electron release energy as photon and when as mechanical vibration?

Suppose we have a compound which has been given energy(either in the from of heat or light). Now, its electrons would absorb this energy and kick up to a high energy level. But, it would also re-emit ...
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Do atoms absorb the same amount of light?

I'm currently working on a project on my own where I'm interested in finding information about an object based on a spectrum. Namely, I want to use the spectrum that I input into my program to be able ...
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Why isn't thunder muted or softened by rain drops?

I watched a documentary showing how NASA applied water droplets to absorb the huge amount of sound energy when the rocket is ignited at launch. So, how come billions of rain drops don't seem to mute ...
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Rate of Photon Absorption in a Semiconductor - Fermi's Golden Rule

In this paper, the rate of photon absorption in a semiconductor is given by Fermi's golden rule: $$ w_{1,2} = \frac{2\pi}{\hbar}\frac{e^{2}}{m^{2}c^{2}}\frac{2V}{(2\pi)^{3}}\int_{B.Z.}|\mathbf{A}\cdot\...
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Absorption and emission spectra

I had this exercise on a test the other day and I still don't know how to solve it. Being given the image below, I have to say what's the type for each spectra, absorption or emission. I didn't find ...
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Nonlinear Absorption Coefficient

How is Absorption Coefficient related to Susceptibility. I want to find linear, 3rd and 5th order absorption coefficient from linear, 3rd and 5th order susceptibility.
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Is it possible to achieve Invisibilty? [closed]

I read that mirrors absorb only a small amount of light(1-2%). And recently MIT engineers developed the "Blackest Black"(blacker than Vantablack) which reflects only 0.005% of the light. Let's say we ...
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Absorption given a complex refractive index

I'm learning about complex refractive index, and I know it has something to do with absorption, so a light wave which is propagating in $z$ gets absorbed by the following law: $$e^{- \frac{2 \pi}{\...
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Can electrons transition within energy bands, or must they transition from one band to another?

A while back, I asked a question about the absorption of different wavelengths by matter (see this post). I received some excellent answers that prompted to undertake some more in-depth research, ...
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How do metals reflect electromagnetic radiation?

Microwaves, for example, can be reflected off metallic surfaces. This seems counter-intuitive, since the metal's electrons could interact with the electric field component of the EM wave and absorb it....
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Absorption spectrum of hydrogen atom

In absorption spectrum of hydrogen atom, only one electron is present in its one atom which is in ground state, so it means that all electrons can only absorb energy of photon of wavelength which lies ...
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Recoil velocity of atom after photon absorption

I'm trying to calculate the recoil velocity of a stationary atom after absorbing a photon, in terms of $E$ and $m$. I've tried manipulating relativistic equations, keeping in mind conservation of ...
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How can an object absorb so many wavelengths, if their energies must match an energy level transition of an electron?

I believe I have a misunderstanding of some principles, but I have not, even through quite a bit of research, been able to understand this problem. My current understanding of transmission, ...
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Why does the real part of cavity transfer function equal the squared magnitude of cavity transfer function?

The normalized transmission transfer function for an optical cavity is something like $$ T(\Delta) = \frac{\frac{\kappa}{2}}{\frac{\kappa}{2} - i \Delta} $$ Here $\Delta$ is the frequency detuning ...
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Is reflection just a re-emitted wavelength at the electronic scale? Does reflection require absorption in the first place?

I'm researching on how different wavelengths choose to either reflect, get absorbed, or transmit through a particular material. I've read that transmission is when waves do not interact with the ...
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Electrons only affected by electric field of EM wave misconception?

When an EM wave is vertically polarised, and an aerial vertically aligned, a signal is received because it is in the correct alignment to absorb the wave that is vertically polarised (relative to the ...
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Emission of heat from absorption of light photon

So I've recently learned about photoelectric effect. It made sense at first, but when I try to combine it with what I thought I knew about emission and reflection of photon, things become rather messy....
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How to find the fraction of light absorbed by a surface?

How to find the fraction of light absorbed by a surface? What values do we need? I am trying to find the fraction of light absorbed by a surface when it's dry and when it's wet. I have something ...
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How to find the probability reflection at a liquid-air interface for a surface which reflects diffusely according to Lambert's law?

The smooth surface is air-liquid interface and the rough surface is let's say a t-shirt. The image above shows the probability of each reflection, and the $p$ value is the probability of the light ...
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Why can atoms only absorb/emit certain frequencies of light?

I'm aware that the orbitals of atoms have discrete energy spectra. The energies must obey the atom's Hamiltonian eigenvalue equation $H|\psi_n\rangle=E_n|\psi_n\rangle$ and this only holds for certain ...
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Derivation of Optical Absorption Coefficient in Semiconductors

I have been researching how to derive an expression for the absorption coefficient in semiconductors. I know the absorption coefficient can be expressed as such $$\alpha = A(hf-E_g)^{n}$$ with $n = \...
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Imaginary part of semiconductors index of refraction

I understand that the index of refraction is complex and can be expressed as such: $ \widetilde{\eta} = \eta + i \kappa $. However I’ve been searching for a bit and I am unable to find the derivation ...
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How is absorption integrated in the simple Drude model?

What is the physical process of absorption in the Drude model? As far as I understood in the Drude model you only consider the electrons as classical particles and frozen ions. No other particles ...
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How does the attenuation coefficient of white light in water compare to the attenuation coefficient of monochromatic light in water?

So, from what I understand, different wavelengths of visible light, when shone through water, will have different attenuation coefficients due to scattering and absorption from the water molecules. ...
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What happens to oxygen during atmospheric absorption of radiation with a peak at 60 GHz

This question discusses atmospheric absorption of radiation (specifically 5G radio waves) due to oxygen at 60 GHz. I would like to know exactly what happens to oxygen in all its forms (be it air or ...
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Are there anti-reflective paint other than black matt paint?

I am trying to build a box where I will be testing some materials inside the box to take measurements of the irradiation. I need to make it so that the walls of the box do not reflect any radiation (...
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Why do satellite methane detectors use some spectral lines and not others?

I was reviewing absorption/transmittance spectra and was wondering why certain wavelengths are chosen for detectors and not others. Take methane for example For small electronic IR detectors they ...
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How to picture vibrational overtones of water?

Im trying to understand the colour of water. The absorption occurs because of some of the vibrational overtones of water. The absorption band at 698 nm (14300 cm−1) is a 3rd overtone (n=4) The ...
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Absorption cross section for Nitrogen in the visible spectrum

I am trying to find data for the absorption cross section of Nitrogen at various wavelengths in the visible spectrum (~400-800 nm). I can only find data at lower wavelengths, however. Data from the ...
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Momentum matrix elements for two-photon absorption in semiconductors

I am trying to follow the paper "Two-photon absorption with exciton effect for degenerate valence bands" (to be found here: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.9.3502). It gives the ...
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How does a spectral line tell us about the magnetic field of a star?

An absorption line in the spectrum can indicate the abundance of a chemical element in a star; but according to NASA, it can also tell us about the magnetic field of the star. Can a spectral line ...

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