Questions tagged [absorption]

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

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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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Cound someone help to check if this paper is talking about sound absorption coefficient of the air?

I am trying to compute the distance I stand away from a sound source and still can detect the sound although I cannot hear clearly what the speaker is saying. Given the threshold of human hearing and ...
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How does the wave model of light account for absorption?

I'm working on a blog post about wireless communication, and comparing the wave and particle models of light. I want to answer the same set of questions from the viewpoint of each model. One of these ...
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Relation between energy, frequency and wavelength [duplicate]

Frequency $f$ and wavelength $\lambda$ of light don't alter after reflection. If that is the case, then energy should also not alter after reflection as $E=h f$. But energy gets altered after ...
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How can energy be conserved in photon absorption at a detector?

This question is somewhat of an elaboration on the discussion here, which didn't really get a satisfactory answer. A related (but not identical) question of mine is found here, which also was not ...
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Two state system interaction with radiation - exact solution

Edited after comments. I can't seem to find (or derive) the exact solution of the two quantum state system absorption problem in the following formulation. Let's consider the general harmonic wave ...
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Why exactly does a material reflect/absorb/refract light? [duplicate]

What is the property of the molecules of the material that causes it to behave differently when it interacts with light. Is it the frequency of the material? I was thinking that the resonant ...
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Below what threshold of intensity can a ray of light be considered absorbed?

Say I have a beam of light of intensity I. I'm modeling its traversal through a medium which absorbs light. As it travels, I reduce its strength by a certain specified factor. Below what intensity ...
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How do I calculate light transmittance given the absorption coefficient and thickness of the medium?

I would like to know the percentage of light that makes it through a glass pane, and I'm given the absorption coefficient and the thickness of the glass. The glass is non-reflective if that helps any....
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Does vacuum absorb electromagnetic waves?

Since the refractive index of vacuum is real, this is highly unlikely. However, it seems that it does following the absorption per unit volume defined in terms of the Poynting vector: \begin{equation}...
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Transmission Spectrum of Rock

Maybe a very specific question, but what wavelengths are sand grains transparent to? Also, how can one image underground minerals through rock? Is there a certain Infrared band that sandstone (...
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$CO_2$ absoprtion bands in atmosphere and impact of increasing concentration levels

I have a question to do with this graphic and the CO2 absorption band highlighted with a red vertical line. The image shows that nearly 100% of the IR energy in that band is absorbed in the ...
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Are absorption and attenuation the same thing?

Are absorption and attenuation different words for the same thing? Wikipedia separate has articles on Absorption (Acoustics) and Accoustic Attenuation. I don't see a clear physical distinction between ...
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Interpretation of the photon scattering rate?

The photon scattering rate $\Gamma$ describes the rate at which photons scatter off an atom$^1$. In a two-level system, the ansatz for the photon scattering rate often is given by \begin{equation} \...
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Absorption of dark matter by black holes

Our Universe consists of about 22% Dark Matter (DM). Such matter is the main stuff of galaxies. Also, Black Holes (BH) live in galaxies. We know that DM is subject to gravitational interaction. So, ...
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About blocking of microwaves

When a phone is inside microwave oven and if we call it using wifi the phone doesnt recive call as frequency of wifi is same as frequency of wave generated in oven as there is a mesh like thing which ...
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What is the difference between scattering and absorption/emission?

As far as I know, scattering occurs when light excites the atoms or molecules to their higher energy state(virtual state for scattering) followed by emitting photons corresponding to energy ...
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Power absorption - ferromagnetic resonance

Magnetic energy is given by: $$ E(t) = \mathbf{M}(t)\cdot \mathbf{H}(t)$$ Hence, the magnetic power becomes: $$P(t) = \mathbf{M}(t) \cdot \frac{\mathbf{H}(t)}{dt} + \mathbf{H}(t) \cdot \frac{\mathbf{...
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How can atmospheric $CO_2$ absorption of infrared be 100% when its atmospheric concentration is 0.04%?

An absorption spectrum from high in the atmosphere of infrared radiation emitted from the earth, shows that for the 15µm wavelength there is almost complete absorption. This is attributed to ...
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A Problem about Line Broadening and Absorption coefficient

I am reading my textbook, Lasers by Anthony E. Siegman, and I just could not understand a point he made. In the chapter section about inhomogeneous broadening, he used a figure to show the transition ...
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Nature of electromagnetic absorption by quantum and classical systems

Forgive me for lack of formality and possibly incorrect understanding, but hopefully someone can both help to explain the intuition and also add mathematical formalism. In classical electrodynamics, ...
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Can light travel through a maze? [closed]

I want to manufacture a light proof enclosure. I need to understand: if I design a cap with a "U" section profile edge and the body with "T" or "U" section profile edge, will light be able to get ...
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How do materials absorb light

I'm curious how light is absorbed in materials. From what I understand, when an electron absorbs a photon, it gets excited to an energy level that is higher than the level it's in and the energy ...
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Layer of material that transmits light in one direction and absorbs it in the other direction

I am looking for a material (or layer of materials) which transmits light coming from one side and absorbs light coming from the other side. The absorption should be as good as possible and the ...
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Do dieletric mirrors and other reflective surfaces have a maximum intensity to which the absoprtion coefficient increases?

That is, if you shine a laser at a dielectric mirror so that the intensity(photons/seconds*cm^2)becomes sufficiently large, the scattering of the photons off the electrons in the surface atoms becomes ...
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How much heat do colors absorb?

A common grade school experiment is to compare how hot different materials get in direct sunlight. See examples here, here and here for example. The premise is generally two identical objects of ...

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