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Questions tagged [absorption]

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

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Radiation pressure and conservation of energy

TL;DR: How can radiation pressure conserve Energy, given that the atom absorbs all the Energy of the incident photon via its newly excited electron, and stills gains additional kinetic Energy from ...
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Infrared pass material thermal camera

I have a situation in which I need to use a thermal camera in a rain enviroment, the camera is mounted on a gymbal and can rotate 360 degrees, so I tought it may be an option to build a dome in order ...
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Reduced absorption coefficient question

I came across a paper that reads It is noteworthy that for a sample without lateral light propagation in the material, i.e. [reduced scattering] $\mu_s' = \infty$ and [absorption] $\mu_a=0$, ... ...
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What is Dipolar Dissipation?

When light hits an object, a part of it gets absorbed. Sometimes, people refer to that as "dipolar dissipation". What do they mean exactly by that and does it apply for all materials ? Thanks.
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Power absorbed by electron in plane electromagnetic wave

How can the power (in Watts) absorbed by the electron be calculated, knowing the incident electric field amplitude $ E_0 $, wavelength $ \lambda $, and the electron momentum relaxation time $ \tau $ ...
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What happens to the spin when photon is absorbed by an electron?

Photon is spin 1 and electron is spin 1/2, so when a photon is absorbed by an electron it is destroyed and the electron becomes excited by that amount of energy. The next moment the electron will go ...
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Numerically Stable Light Absorption Density Calculation

I am reading through the documentation provided by Lumerical concerning light absorption per unit volume : https://kb.lumerical.com/layout_analysis_pabs_simple.html Lumerical says that: It can be ...
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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 the ...
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Why should blackbody radiation emit all the absorbed energy?

So it is said that a perfect blackbody absorbs all the energy and then emits all of that in the form of blackbody radition. Why should it emit all the absorbed energy? Why can it not emit some and ...
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Spectrum of Dielectric Function along Energy

What do the peaks and troughs in the spectrum of the dielectric function (real and imaginary parts) along energy indicate? I understand that the real part represents the polarization and the imaginary ...
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Evanescent wave in absorbing medium

Classic setup : Reflection and refraction with Snell-Descartes' law. Having 2 medium (1 and 2) with the normal n being oriented from 1 to 2 and placing ourselves in the incidence plane, we assume n ...
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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 ...
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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 ...
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67 views

Where does the momentum go when atom absorb a photon? [duplicate]

Imagine an electron around an atom absorbs a photon and becomes excited, it has now jumped to a higher orbital. At this point in time, where does the momentum of the photon goes?
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Raman effect and IR absorption

Let's consider a molecule with N atoms, on which is shot a polychromatic IR beam. From the quantum selection rules, we know that in a single event of absorption only one of the 3N-6 oscillators can be ...
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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 ...
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If the electric force is the exchange of virtual photons, how can free electrons be accelerated by it?

I know that free electrons can't absorb photons. It is, however, known that electric forces can accelerate electrons. But if electric interactions are merely an exchange of virtual photons, how can ...
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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 painting ...
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“For every line in absorption spectra, the corresponding emission line is present, but the reverse is not true”

I was studying atomic physics and read the line for every line in absorption spectra, the corresponding emission line is present, but the reverse is not true and I am not able to understand it ...
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How does the reflection coefficient change with scattering and absorption?

My professor of Biomedical Optics course asked us to think upon the evolution of the reflection coefficient with the absorption coefficient $\mu_a$, the reduced scattering coefficient $\mu_s'$ and the ...
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2answers
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If EM waves of radio range can pass through large obstacles, why antennas do receive them? [closed]

For example a tiny antenna in the phone, why em wave do not pass through it, but pass through concrete walls?
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Frequency domain theory for absorption and scattering tomography

TL, DR: in the theory absorption and scattering tomography it is possible to obtain a formula for the field in a detector point once it is known the position of the source and the inhomogeneities of ...
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What is the difference between upconversion and two photon absorption?

I have read this: https://en.wikipedia.org/wiki/Photon_upconversion And it says that upconversion is a process where subsequential absorption of two or more photons leads to emission of light with ...
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Complex refractive index and absorption

I have a quite plain and simple question: Why is the imaginary part of the refractive index negative? I read it is to allow a positive sign in case of absorption. But how/why? I don't see why it ...
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Fresnel equations & emission

As part of a project work I had to derive the absorption of a thin-film stack. It was a semiconductor between two oxides on a metallic back reflector. I used Fresnel equations and optimized the ...
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What is difference between transmission and transparency?

I learned about the spectral hole burning. On Wikipedia, it said Spectral hole burning is the frequency-selective bleaching of the absorption spectrum of a material, which leads to an increased ...
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Absorption spectra

I would like some help understanding absorption spectra, for example, by a cloud of gas in space. Photons might be absorbed if their energy matches a transition in one of the atoms or molecules in ...
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Absorption of high frequency waves

Sources have stated that high frequency EM waves are absorbed by particles in the atmosphere (such as water) more easily than low frequency EM waves. Why does this occur? Does it have anything to do ...
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What happens if we re-excite an excited electron to a higher energy level?

What happens if we re-excite an excited electron to a higher energy level? e.g. we excite hydrogen's electron from n=1 to n=3, then before it gets to return to the ground state, we hit it with ...
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1answer
103 views

What is the meaning of a Fourier Transform in an electric field $E(\omega,t)$?

There is this electric field in one dimension: $$ E(\omega,t) = E_0 \cos(\omega t) $$ It is reaching the surface of a semiconductor. The number of photons reaching the surface per unit of area is ...
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How linearly additive are the x-ray mass attenuation coefficients for molecules?

Having a look at https://www.nist.gov/pml/x-ray-mass-attenuation-coefficients, the introduction states: For compounds and mixtures, values for $μ/ρ$ can be obtained by simple additivity, i.e., ...
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how to calculate the absorption spectrum for a given element?

I made a spectrometer that gives the absorption spectrum, by comparing the before and after readings. There are lots of information on the emission spectrum of elements, but I need the absorption ...
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from a spectrometer, how to determine unknown substance in water?

I created a spectrometer that produces nice clean wavelengths, I calibrated it using a fluorescent bulb. from that I can create a graph from the data. after which, I use the known position to of ...
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How does silver affect transmission of energy in the visible and infrared part of the spectrum?

A common method to prevent radio frequency and microwave energy from going through windows is to apply a microscopic layer of silver to the surface of the glass, either by attaching a film coated with ...
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Cause and description of 'secondary' probability peaks in Above Threshold Ionization

While reading about above-threshold ionization, I found this graph on the wikipedia page about ATI: The $x$ axis represents the kinetic energy of the electron and the $y$ axis shows the ...
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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 ...
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White hotter than black

Black color substance is assumed to absorb all the light/radiation that falls on it. White color substance on the other hand, reflects all the radiation that falls on it. Since all the momentum of ...
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Solving the Radiative Transfer Equation for Different Materials (in the Visible Light Regime)

Using the radiative transfer equation $(\vec{w}\cdot\nabla)L(\vec{x},\vec{\omega}) = -(\sigma_{a}+\sigma_{s})L(\vec{x},\vec{\omega})+Q(\vec{x},\vec{\omega})+\sigma_{s} \int_{\Omega}L(\vec{x},\vec{\...
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Do objects reflect light of their own color based off constructive wave interference?

Note: Why objects reflect light of their color is already answered here: Physics of color: why do visible colors absorb all colors except the color itself? My question is whether my following theory ...
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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 ...
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Is there some literature where diffusing molecules have to encounter a reflecting boundary which is absorbing at some places?

I am familiar with the concept of diffusion with reflecting and absorbing boundary in 1D. My question is, is there a way by which we can write Green's equation for a boundary, in 2D, that is primarily ...
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Does photon absorption annihilate the associated EM wave instantly?

My Understanding A single photon has an associated electromagnetic wave. The wave is spread out in space, but the photon is considered a point particle. If the photon is absorbed, the entire wave ...
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Absorbing only a fraction of photon energy

Atoms have energy levels for its electrons. When there is a match between those and light photon energy, an electronic transition ocurrs. Question Why atoms can't absorb just part of a photon ...
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How do you calculate the recession velocity?

$$ \begin{alignat}{7} && \frac{\Delta \lambda}{\lambda} & = \frac{v}{c} \\[2.5px] &\therefore & v & \approx \frac{\Delta \lambda}{\lambda}c \end{alignat} $$ If you want to find ...
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Why walls are blocking infrared waves? If bricks absorbs only certain infrared frequency as shown in the infrared absorption spectroscopy graph below

link to the pdf I am told that infrared is reflected(blocked) by wall. my argument is,how can they reflect a photon if they don't absorb it.as you know infrared is absorbed by molecule which has same ...
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Optical conductivity: Does higher real part mean higher losses/absorption?

My question is with regards to the relationship between optical conductivity and optical permittivity. Since the imaginary part of optical permittivity signifies losses/absorption, the real part of ...
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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 ...
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Hypothetically, if there was a substance that could absorb all visible light and reflected none, how would it appear to the human eye?

Would said substance just be perceived as a "hole" in our vision, if it was capable of absorbing 100% of all light? Also on a side note, would the absorption of all light instead of only visible ...
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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 ...