Questions tagged [absorption]

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

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Paint: "Darker When Dry"?

A great question I enjoy bringing up is why are things, in general, "darker when wet". This applies to porous and granular materials like wetted stone, paper, sand etc. It also comes up in ...
mittimithai's user avatar
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How can daylight have a higher colour temperature (e.g. 6500 K or D65) than sunlight in space?

Supposedly, daylight at midday has a colour temperature of 6500 K. This reference is also the standard for calibrating computer screens (that's how I fell into this). However, outside the atmosphere ...
OsthatoAlfakyn's user avatar
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Complex part of second-order susceptibility in nonlinear optics

In optics, the absorption of photons by a material can be described by considering the material's susceptibility. For linear absorption (involving a single photon), we think about the imaginary part ...
Liz Salander's user avatar
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What causes materials like Vantablack to have their high optical absorption properties?

As per the title of this post. From reading, I understand that blackbody radiation is a factor I should consider here, with light being absorbed and converted to heat etc. However, what I want to ...
Jenson Holden's user avatar
4 votes
2 answers
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Times associated with absorption and emission processes

I am currently reading the book "Advances in Atomic Physics: An Overview" by Cohen-Tannoudji and Guéry-Odelin. In pages 29-31 the authors discuss a two-level atom subject to a broadband radiation ...
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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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Relationship between oscillator strength and cross-section

In the context of absorption of photons by atoms, I have come across two seemingly very related quantities, cross section and oscillator strength. In the book Physics of the Interstellar and ...
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What is the relationship between emissivity $\varepsilon$ and the imaginary part of relative permittivity constant $\epsilon^{''}_{\rm r}$ if any?

In terms of the Stefan-Boltzmann law a body that does not absorb all incident radiation emits less total energy than a black body and is characterized by an emissivity $0<\varepsilon <1$ such ...
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Two Photon Absorption dependence on Semiconductor Band Gap

It's well known that Two Photon Absorption coefficient is scaling with $E_g^{-3}$. Does anyone know what is the physical reason for this scaling? What is the physical theory behind this mathematics?
user31173's user avatar
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Physcial interpretation of term neglected in Rotating Wave Approximation

Consider an atom as a two-level system $|1\rangle, |2\rangle$ with energy separation $\hbar \omega_0$, which is interacting with a classical electric field $\vec{E}=\vec{E}_0 \cos(\omega t)$. This ...
Welcome_Green's user avatar
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Predict color of dye under a certain wavelength of light?

I am picking fluorescent dyes to be put under a UV of known wavelength and would like to be able to predict approximately what color the dyes will appear under the light. I can request ...
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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 ...
Duckfeet's user avatar
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Can water be made more violet?

Water is intrinsically blue because of molecular vibrations. The topic is covered here: Only sea water appears blue in color, why this is not happening in river water? And here, which I post ...
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Feynman’s Treatment of an Opaque Wall

First time poster. I’ve been reading Feynman’s Lectures on Physics, and I’ve just finished reading his treatment on diffraction. Feynman described a method of thinking about an opaque wall that was ...
user218912's user avatar
2 votes
2 answers
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In diffraction When wavelength is less than slit width then does the scattered light gets absorbed & emitted from the wall or just rebound?

I know that when the slit width is less than that of wavelength then the slit will act as a point source and scatter the light in all directions. But my question is that during the scattering of ...
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Rate of direct (non-thermal) photon-induced evaporation of water?

I have read a long time ago of early experiments in the evaporation rate of surface water, and a discovery that in addition to the Sun's impact on the temperature of the water, it was believed that ...
uhoh's user avatar
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given an AC field, how many photons are there?

Say you are applying a time varying potential across double quantum dots in the form of $V_{ac}$cos($2\pi f t$). We know that each photon has an energy $E_{photon}= hf$. Is it correct to say that ...
Blackwidow's user avatar
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Partial absortion of a photon

In atoms, there are electronic energy levels, when there is a match between those and a light photon energy, an electronic transition ocurs. Example and question Suppose an atom has a levels $0$, $1$...
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Light Inside a Spherical Droplet

Suppose that a monochromatic light beam of wavelength $\lambda$ bounces around inside a perfectly spherical droplet of glycerol (radius $r$, refractive index $n$, density $\rho$, molar mass $M$) ...
The Riddler's user avatar
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Why does it take time for absorption to set in?

I read this sentence in Optics Principles and Applications by Sharma regarding light dispersion: But since it takes some time for the absorption to set in, the trailing edge of the pulse is ...
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Book on spectroscopy (line dependency on parameters)

I am trying to find a book (undergraduate level) on Spectroscopy. I am interested in how molecular absorption lines depend on parameters like temperature and pressure (for example with gases). Can ...
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Connection: Work on dipole <-> optical absorption

If I consider a two-level system with a ground and an excited state, I can compute the instantaneous rate at which work is being done on the dipole $\mu(t)$ by an electric field $E(t)$: $\dot{W} = E(...
DaP's user avatar
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The resolution limit for lithography in practice?

For a given wavelength of light $\lambda$, and a given numerical aperture (NA), I always see the statement in papers/etc. that we can perform lithographic patterning at the Rayleigh limit given by $\...
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Einsteins Coefficient of Absorption in solid state

What solid state parameter determines the probability of absorption (Einsteins coefficient B) in a material? Is it material dependent? I think, I cannot say bandgap. Because if I have a source having ...
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How much gas is needed to produce absorption lines?

I am trying to know whether it would be possible to do an undergraduate laboratory experiment to measure absorption lines produced by a gas. The idea is to have a background source of light with a ...
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Absorption Cross Section for Two-Level Spin System in an AC Magnetic Field - Photon Picture

For a two-level spin with a energy difference of $E = h f$, where the two levels have zero dipole electric coupling and can only be driven by a magnetic field, how do I calculate the absorption cross ...
SpinSensor's user avatar
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How does light absorption work for solids and liquids?

I've studied in my physics class, absorption and emission spectra for gases or more "spread out" molecules like what is done in atomic absorption spectroscopy (learnt that one in chemistry). ...
user377561's user avatar
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How to get Absorption cross section of Gaseous Ions for photons?

How or where can I find the Absorption cross-section of Gaseous Ions? I have looked over the internet and can only find it for neutral atoms. Does it increase or decrease for ions? I have found ...
Aditya Lal's user avatar
1 vote
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31 views

Photon absorption in different layers

Let's suppose that space is divided into different regions: for $x < 0$ there is just vacuum space; for $x$ between 0 and $t_1$ space is filled with a material of type 1; for $x$ between $t_1$ ...
Antonio19932806's user avatar
1 vote
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How is black body radiation from sample eliminated when measuring absorption coefficient?

I wonder how absorption spectra of a sample (e.g. gas with some $CO_2$ absorbing strongly at $\approx 15\mu m$) is measured by IR spectroscopy, thereby having in mind the following arrangement, ...
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Can anybody explain this Beer-Lambert's law condition for it to be valid?

"The incident radiation should preferably be monochromatic, or have at least a width that is narrower than that of the attenuating transition. Otherwise a spectrometer as detector for the power ...
Ireneo de la Cruz Jr.'s user avatar
1 vote
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Identifing a formula for the contribution of IR scattering to the permittivity of metals

I'm using a software modelling the complex refractive index of different materials in the THz/far infrared frequency range. One of the parameters that the user can add to the model of the permittivity ...
elyuku's user avatar
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What is the energy difference between the 3d 4s valence subshells of iron (and copper)?

In gold, for example, the energy difference between the 5d 6s valence subshells is ≈ 2.7 eV (that's why it has color). But what about the 3d 4s subshells of iron and copper? What are their energy ...
Walter Grosse's user avatar
1 vote
0 answers
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Absorption spectra Oxygen vs temperature

Whilst recently commissioning a spectroscopic Tunable diode laser "Oxygen Analyser" on a waste-to-energy plant, I wondered how the Analyser (which fires a narrow wavelength laser across the ...
scott hookway's user avatar
1 vote
1 answer
73 views

Are there certain EM frequencies that are impossible to emit?

Every element has absorption lines. Is there some line which is not covered by anything else? Some strange gap in the universe?
Euphorbium's user avatar
1 vote
0 answers
65 views

Absorption rate vs. Einstein Absorption Coefficient

I am trying to understand the absorption rate (or absorption probability density), which is defined as $$p_{ab}=\frac{\sigma c}{V}, $$ where $\sigma$ is absorption (transition) cross section and $V$ ...
Andris Erglis's user avatar
1 vote
1 answer
37 views

Laws for light absorbtion

When light of one particular wavelength is directed to a surface, it may get completely or partly reflected, or completely absorbed. Is the amount of reflected light always proportional to the ...
Nico Schlömer's user avatar
1 vote
0 answers
51 views

Is liquid lead better gamma ray absorber than solid lead?

Is liquid lead better gamma ray absorber than solid lead? Can this be compared with the fact that an el.conductor has more resistance to current at higher temperatures? If yes could it be used in ...
Janko Bradvica's user avatar
1 vote
0 answers
16 views

Is the capacity of absorbtion of gamma rays by a material dependent on its temperature?

Is the capacity of absorbtion of gamma rays by a material dependent on its temperature? As electrons heat up a wire that wire increases its resistance to the current. Is it same regarding gamma ray ...
Krešimir Bradvica's user avatar
1 vote
1 answer
65 views

Requirements for Z-scan or I-scan measurements of nonlinear optical materials

I am looking to understand what requirements there are for any version of Z-Scan technique or the I-scan technique. These techniques are used for measuring nonlinear absorption and nonlinear ...
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Why planet's absorption spectrum works

So I've come across this image somewhere on the internet. My understanding of how people determine what's in the atmosphere of distant planets is that the local star (which has a continuous spectrum) ...
157 239n's user avatar
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1 answer
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Why do electrons in a cool gas not release photons as they are excited?

When white light is shone on a cool gas the electrons absorb photons of a certain wave lengths and become excited. Shouldn’t the electrons then return to ground and release photons with the same ...
jfearn's user avatar
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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 ...
Haorong Wu's user avatar
1 vote
1 answer
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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 ...
user44756's user avatar
1 vote
0 answers
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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 (...
Joeseph123's user avatar
1 vote
0 answers
251 views

List of complex refractive indices for various frequencies and various materials

I want a list of refractive index values for various materials (or even a single material) for various frequencies / wavelengths (I need this specifically for the micro wave - radio wave regions of ...
1 vote
1 answer
504 views

Plasma Frequency of Indium Tin Oxide

What does determine the plasma frequency? The formula is: $$\omega_p² = \frac{4 \pi N e²}{m}$$ and for frequencies above the plasma frequency the material is transparent. So for indium tin oxide (...
isa's user avatar
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How would gray dust work, on a microscopic level?

I came across an article on something called gray dust, a hypothetical substance explored theoretically during the early 2000s. It attempted to explain cosmological supernova observations by ...
HDE 226868's user avatar
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What are some mechanisms that can lead to unexpected/anomalous spectral lines

I am studying fluorescent spectroscopy (laser-induced fluorescence spectroscopy specifically). In a particular atomic spectrum, there are some unexpected lines not associated with any known ...
peasqueeze's user avatar
1 vote
1 answer
173 views

The Attenuation of Light

I have this question: Show that the attenuation of light as it travels through the interstellar medium follows an exponential law My initial thoughts were to demonstrate the absorption of ...
LightningStrike's user avatar