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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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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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Potential energy surface for a diatomic molecule desorbing from a surface

I have been asked to sketch the potential energy surface as a two-dimensional contour plot as a function of the vertical distance between the center of mass of A2 and the solid S, and the internuclear ...
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Photon-induced evaporation rate of water (non-thermal)?

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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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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Extracting the absorption of a thin film layer

I am currently working on a problem, where i want to calculate the absorption of a semiconducting 2D-material which is sanwiched between two dielectrics and based on a mirror. The stack is therefore: ...
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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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Trouble understanding difference Stokes and Anti-stokes

First, I have been trouble by so many Scattering and absorption event descriptions that stall my understanding of differentiating between each. I understand that Stokes is an absorption event. Two ...
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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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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 ...
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Where can one find information about damping coefficients for electronic transitions in atoms?

I understand that the index of refraction for a given atomic species with number density $N$ near a single electronic transition associated with frequency $\omega_0$ given by $$ n(N,\omega)=1+\frac{...
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Two-photon absorption fluorescence of air

I'm wondering if there are any major constituents of air which are capable of undergoing two-photon absorption and ultimately fluorescing in the visible spectrum. The original wavelengths of the ...
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Is there an advantage in stacking scanning beams in the opposite directions in tomography?

For example in this hypothetical tomography chamber (beams on other planes in this chamber ommited in drawing). On the left emitters are only on one side and receivers on the opposite side. On the ...
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Average distance travelled before absorbtion 253 nm photon in air

At first I wanted to use term "Mean free path" in title but I know it means other kinds of interactions too,not just absorbtion.What I really mean is mean free path but only for absorbtion. For ...
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How to calculate photon absorbtion in gas

Imagine 1 cubic centimeter of ozone at atmosferic pressure,UV laser beam with 255 nm wavelenght,1 Watt power and square beam shape strikes the ozone cube,how much energy gets absorbed into ozone? ...
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Dielectric constants from refractive index and absorption spectra

I would like to calculate the dispersion relation (dielectric constants $\varepsilon'$ and $\varepsilon''$) from two spectra: refractive index $n$ and absorption (in %). I tried to use the relation $$\...
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Cosmic ray shielding for electronics on Earth

There are plenty of topics discussing cosmic ray shielding, but they all put emphasis on spacecraft shielding, where things like radiation and mass are a big problem. So I decided to ask a question ...
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Is infrared radiation more easily absorbed than visible light?

Some background: I am curious if infrared lamps used in hatcheries and bathroom fixtures offer any advantage over ordinary incandescent bulbs. A 40 watt bulb produces the same amount of energy, ...
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Photon Absorption and Emission of Fluorescein (calculate)

For the beta-carotene one can see that there are 22 free electrons and we can model its absorption and emission dua to the infinite potential well (particle in a box). Due to the pauli principle, we ...
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Measuring the heat absorbed by objects close to a radiator

I have a digital piano 12"/30cm to the side of a radiator (not in front of it). Radiator is 60°C as measured on an infrared (IR) thermometer, air temperature around the piano is 16-17C with the ...
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Why are some materials dull rather than shiny (cloth, coal, matte paint etc.)?

The converse of this question is perhaps "why are metals shiny". From what I understand, metals are covered by a sea of free electrons that oscillate in response to incident light/EM wave, and the ...
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Emission and Absorption in color

This may be a really simple question: If electrons only absorb specific wavelengths of light and then emit them and that’s how we see color, but what happens to the other wavelengths? Without them ...