Questions tagged [absorption]

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

Filter by
Sorted by
Tagged with
0 votes
1 answer
16 views

Where can I find photon absorption cross-sections for various isotopes?

I am looking for absorption cross-sections for photons. Usually, I am dealing with neutron absorption where I utilize https://www.nndc.bnl.gov/endf/ for my data. This is a really handy website that ...
user avatar
3 votes
1 answer
151 views

Sunscreen protection, SPF, and amount applied: relationship?

In the article How SPF Changes with How Much Sunscreen You Use (last updated Dec 29, 2017), the author says that it is disturbing that insufficient sunscreen (in theory) decreases protection ...
user avatar
  • 542
0 votes
1 answer
43 views

Why does light behave differently when interacting with multiple particles?

When light hits an atom (I will use a carbon atom for simplicity), if it is not in the absorption and/or emission spectrum of carbon, it will simply pass through without interacting with the atom. ...
user avatar
0 votes
0 answers
28 views

Why does light not pass through opaque objects? [duplicate]

Since light is massless it does not interact with particles unless that specific wavelength is on the emission and absorption spectrum. The emission and absorption spectrum of an atom indicates the ...
user avatar
0 votes
0 answers
25 views

Why water bearing clouds come black to the eyes? [duplicate]

Why water bearing clouds come black to the eyes? As far as I know mist is whitish, and rivers and seas are relatively transparent...Why the water inside the cloud absorbs all wavelengths?
user avatar
3 votes
0 answers
51 views

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 ...
user avatar
0 votes
0 answers
11 views

Why is the bound-free opacity proportional to $Z$?

I've seen the following formula repeated in multiple places, including wikipedia that the bound-free opacity is proportional to the metalicity $Z$ $$ \kappa\approx 4.34\times 10^{25}\frac{g_{bf}}{t}Z(...
user avatar
  • 1,188
0 votes
0 answers
20 views

How does wavelength affect scattering?

Let's say that I have a detector and a few sources of light (think lightbulbs). The sources are all the same power and emit different colours of light. We're on the surface of Earth. As I walk further ...
user avatar
0 votes
1 answer
41 views

Effective optical depth using Beer-Lambert law for non-linear attenuation?

Currently I have a gas with a density that follows and inverse square law in distance, $r$. Given that I know the mass attenuation coefficient of this gas, I wish to calculate an effective optical ...
user avatar
1 vote
0 answers
22 views

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 ...
user avatar
0 votes
0 answers
11 views

Extracting a mass attenuation coefficient for a dilute metallic gas for visible wavelengths

Currently, I am examining the attenuation of a visible wavelength laser with an initial intensity, $I_0$ by a metal vapor (in this case Aluminium) that has a density, $\rho_g$ of around 0.02g/cm$^3$. ...
user avatar
0 votes
0 answers
22 views

How does reflection polarise light on the atomic level?

From my reading when light is reflected S-p polarisation occurs with the reflected light being parallel to the surface in polarisation and the mixed light being transmitted through. Light is absorbed, ...
user avatar
-2 votes
1 answer
53 views

Classically, is the notion of a photon superfluous according to special relativity?

The invariant spacetime interval of a lightlike path is zero. So a photon is always exchanged between particles that are actually zero interval from each other. Then, is the concept of the photon ...
user avatar
  • 1,383
1 vote
2 answers
50 views

Absorption vs emission not in thermodynamic equilibrium

I have read that good absorbers are good emitters. The argument goes that at thermodynamic equilibrium, the amount of radiation a body emits must be the same as it absorbs, otherwise the body will ...
user avatar
-1 votes
2 answers
60 views

Does carbon dioxide absorb visible light to any degree?

Does carbon dioxide absorb visible light to any degree? I found this: https://www.dinosaurtheory.com/thick_atmosphere.html and I wondered whether several hundred atmospheres worth of CO2 really would ...
user avatar
  • 1,344
1 vote
1 answer
36 views

When does an emitted photon produce recoil in the emitting atom?

I ask because I've always thought that the wave equation of the departing photon would be (barring nearby mirrors or absorbers) a sphere of wavelets growing out from the emitting atom at lightspeed. ...
user avatar
2 votes
1 answer
62 views

What colour are metals? [duplicate]

I know that glass is actually green in that mirrors will always leave a green tint. This is because, although it's a small margin, green is the most absorbed wavelength for glass. Following on from ...
user avatar
  • 2,563
0 votes
0 answers
13 views

List of lowest ground state energy transitions for all elements

Do you know of a list of the lowest ground state (s-p) transition for all/most/some of the periodic tables? It would be great if some molecules were included in this (water, CO2, etc). I am after ...
user avatar
0 votes
0 answers
19 views

Difference between photoluminescence spectra, scattering and absorption of light by a nano particle?

If light is incident on a nano-particle, then what are the differences between the phenomena that occurs afterwards such as scattering, absorption and photoluminescence (PL) spectra. Though I know ...
user avatar
1 vote
2 answers
54 views

Possibility of combining photovoltaics and solar thermal energy

In a private setting, photovoltaics and solar thermal energy are often harvested on the home's roof and roof area is limited. So, I thought about combining both, i.e. mounting solar collectors ...
user avatar
  • 7,104
0 votes
1 answer
72 views

How do units work when integrating a distribution that has units?

In case some want more context, the source which I'm using (could be wrong...?) is: https://arxiv.org/abs/physics/0202029 (Eqs. 2,5,7) The equations of concern are: $$\sigma_a(\omega) = \sigma_0 g(\...
user avatar
0 votes
1 answer
43 views

Calculating the absorption length of attenuation?

The flux of neutrons is attenuated according to the formula: $$F = F_0 e^{-Ax}$$ And I want to find from the absorption length, defined as the length at which oncoming neutrons is reduced by a factor ...
user avatar
  • 69
3 votes
0 answers
41 views

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 ...
user avatar
  • 699
1 vote
1 answer
79 views

Is photon emission the time-reversed process of photon absorption?

Say we have an atom on which we shoot a photon. Is the process of absorption the time reversed process of emission? I can't imagine the two processes being the same, although in both cases the photon ...
user avatar
0 votes
1 answer
47 views

Is a perfectly-absorbing sphere ill-defined?

Suppose we have a spherical object that absorbs without reflection scalar waves (e.g. sound waves) incident on it. We should expect that the incident wave will get a shadow in the corresponding region ...
user avatar
  • 26.3k
1 vote
1 answer
70 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?
user avatar
2 votes
1 answer
38 views

Absorption spectroscopy - transmittance (normalized)

In the absorption spectroscopy we can calculate transmittance $T$ of a given sample by comparing how the intensity of the incident beam $I_{0}$ is decreased with the distance (Lambert-Beer Law). $A = -...
user avatar
  • 145
0 votes
1 answer
39 views

Hamiltonian of a system of an hydrogenic atom in EM field

In an interaction between an EM wave and an hydrogenic atom (atom with single electron) we have in the semi-classical approximation (I think that's what is called, basically treating classically EM ...
user avatar
2 votes
1 answer
41 views

Why is spontaneous emission neglected in standard discussions of the two-level system?

When discussing two-level systems, spontaneous emission is often neglected `until later'. However, when discussed later, the two-level system is no longer discussed. For example, see Straten and ...
user avatar
  • 1,626
0 votes
1 answer
44 views

Diffusion from bulk to cylinder wall

If D is the diffusion constant of particles, C is concentration, R is the radius, diffusion to disk-like adsorber is 4DRC, and hemisphere is 2piDRC. So what is the diffusion equation to a cylinder ...
user avatar
  • 1
2 votes
2 answers
42 views

Is selective heating of a gas within a mixture possible? Using the absorption wavelength of the molecule

Could you effectively concentrate a particular gas in a mixture by applying only the wavelength absorbed by the target gas? Assuming that the target gas molecules heat up when absorbing the selected ...
user avatar
1 vote
0 answers
25 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 $V$ ...
user avatar
2 votes
2 answers
35 views

Differenciation between wavelength and energy: Does a photons wave-length or energy determine its refraction and absorption?

I know that a photons wavelength and energy are coupled and that my question therefore could be quite ridiculous. However, as a Biologist, I simply learned that refraction is determined by a photons ...
user avatar
  • 121
4 votes
2 answers
92 views

How do we know that the Sun absorbs most of the radiation that falls on it?

The sun is generally considered to be an approximate blackbody. A blackbody has to be a perfect absorber. How do we know that the sun absorbs most of the radiation that falls on it?
user avatar
0 votes
2 answers
68 views

Is it possible that a sufficiently high energy photon can be absorbed by the proton and emitted back without resulting in a fission?

I have read that photons can be absorbed by the protons inside the atom and this would result in a fission, nucleon ejection, or photon emission. Assuming the photon has sufficient amount of energy, ...
user avatar
  • 690
3 votes
1 answer
163 views

Do atoms emit and absorb photons at the same wavelengths?

I know that atoms absorb photons, which promotes electrons to higher energy levels. Then upon de-excitation a photon is released. Is it true that the lines for absorption and emission spectrums are ...
user avatar
  • 128
1 vote
1 answer
34 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 ...
user avatar
6 votes
2 answers
657 views

What is cross section?

I am learning about unit Barn, its unit of cross section. I know it means how likely a particle is to interact with material, its like opacity or transparency in optics. What I dont understand is what ...
user avatar
  • 89
1 vote
1 answer
42 views

Pressure broadening in absorption spectra

I was reading about pressure broadening for atomic spectra. What I can't understand is why it is important in absorption spectra if the collisions affect only the lifetime of the excited states. It ...
user avatar
  • 261
1 vote
0 answers
39 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 ...
user avatar
1 vote
0 answers
12 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 ...
user avatar
1 vote
1 answer
28 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 ...
user avatar
  • 21
0 votes
1 answer
29 views

How to calculate absorbed heat by different painted colours on a steel container?

I'm looking to understand how I can calculate the heat impact in a galvanized steel box with a cooling capacity of $0.25\;\mathrm{kW}$. For example, what is the heating absorption of a box painted ...
user avatar
3 votes
2 answers
575 views

Is a detailed absorption spectrum available for carbon dioxide from 300-1100nm?

I believe that carbon dioxide does not absorb light in the visible region, but is a spectrum available somewhere online that shows this as a fact? As in a straight horizontal line at 100% transmission?...
user avatar
  • 143
0 votes
1 answer
45 views

How do people define the probability of absorption in terms of the size of the universe?

Suppose we are in universe $M$ where we have only a photon $\gamma$ and an hydrogen atom $H$. Let us define the probability of emission a photon by $P_1$ and the probability of absorption by $P_2$. Is ...
user avatar
2 votes
2 answers
141 views

Light reflection, absorption and transmission

According to what I know, reflection, absorption, and transmission all involve the absorption of photon's energy. In the case of reflection and transmission, the absorbed energy is re-emitted in the ...
user avatar
  • 23
4 votes
4 answers
111 views

Does photon absorption occur in discrete packets?

As per the dogma of quantum mech, the jump of an electron from a higher to a lower energy shell is accompanied by photon emission. All photons are born this way. (Although an off topic rebuttal might ...
user avatar
  • 1,681
0 votes
1 answer
224 views

(How) Does temperature affect the light absorption of molecular systems?

My concern is color reflectance spectra that show slightly different characteristics under different sample temperatures. I am trying to find out the reason for this and would like to understand what ...
user avatar
  • 1
0 votes
0 answers
18 views

How does the density of main sequence star impact spectral lines and the depth/width of a spectral line graph?

My understanding is that a denser star will cause the width of a spectral line to broaden and it will cause the depth of the intensity plot to increase (dip lower). Would this be correct? Also, is ...
user avatar
0 votes
1 answer
32 views

Changes in imaginary dielectric function to changes in Absorptivity of material

I have a quick question that I am trying to get my head around. I am the looking at the increased absorption of light in some metal as temperature is increased. Lets say that the imaginary dielectric ...
user avatar

1
2 3 4 5
8