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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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How can the inverse of stimulated emission be distinguished from "normal" absorption?

A simple system with two energy states can absorb an incoming photon (of adequate energy) to get excited, and it can relax by either spontaneously emit a photon afterwards or get stimulated by another ...
Tobias Kienzler's user avatar
2 votes
1 answer
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Is there a way to use the optical transfer-matrix method to determine the absorbance of each layer in a multilayer stack?

I've implemented the transfer-matrix method to determine the the transmittance and reflectance of a multilayer stack of thin films. I know that (ignoring scattering) the absorbance of the entire stack ...
Roy Smart's user avatar
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What is the range of noon sun color temperature, when a light meter reports full expected sunlight (+/- epsilon)?

My question came from trying to find what uncertainty bounds, if any, I can assign to a color temperature sensor, without access to an artifact with a precisely calibrated output spectrum. This leads ...
user3732008's user avatar
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Temporal absorption coefficient from complex wavenumber

A complex wavenumber $k=\beta-i\alpha$ can be defined, that when substituted into a time-harmonic solution $e^{i(\omega t - kx)}$ yields $$e^{-\alpha x}e^{i(\omega t - \beta x)}$$ The first negative ...
korokame's user avatar
1 vote
1 answer
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Absorption spectra in films chemicals & dyes

For a science competition, we have to understand absorption spectra in films chemicals & dyes. But what is that? I've found resources on the absorption spectra of chlorophyll, but I'm unclear as ...
Astrovis's user avatar
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Why escape peak positions are calculated using emission energy and not absorbing energy?

For a X-ray monocromatic source, escape peaks energy positions are described by the difference between the incident energy and the fluorescence ($K_{\alpha}$ for example), like $E_{Escape Peak} = E_0 -...
xor's user avatar
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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 ...
walber97's user avatar
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What happens after bulk gold absorbs a photon with its energy at the band gap or higher (wavelength < 500 nm)?

As is explained in the answers of this question: Why are most metals gray/silver? nicely, the responsible transition occurs between the 5d orbital and the 6s orbital, which is relativistically shrunk ...
Quit007's user avatar
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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 ...
anonymous's user avatar
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4 answers
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Aren't places where geodesics end singularities?

So of course when stuff falls into black holes, the geodesic for anything ends in that singularity. However, isn't it technically true that a light ray that originates from the sun and then hits the ...
Roghan Arun's user avatar
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What determines the wavelength in absorption?

When looking at absorption or reflectance spectra, say in the range of 400nm to 2500nm, you can see peaks (or dips) at certain wavelengths, that are characteristic for the material absorbing and ...
YPOC's user avatar
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Complex Refractive Indices, Absorption, and Transparency

A complex refractive index is defined as $n = n_0 + \kappa$ where $n_0$ is the "standard" refractive index, and $\kappa$ is the optical extinction coefficient. The optical extinction ...
Chris Gnam's user avatar
6 votes
1 answer
110 views

How do we know that the Sun is 71% Hydrogen by mass from emission/absorption spectra?

In my Intro to Astronomy ("intro" is very important, please keep responses as simple as possible) course, we're currently learning about light and electron orbitals and such, and I came ...
Sami Hanna's user avatar
0 votes
2 answers
58 views

Why do the proteins in our eye have a continuous (bell shaped) absorption spectrum?

From quantum physics, I would expect that seeing e.g. red would excite the 564nm energy level of the Photopsin protein. I would also expect to only see (apart from some small smeering out) that we are ...
mtooling's user avatar
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127 views

Where does light energy end up? [closed]

Here's a gedankenexperiment: In situation A you run $P$ watts of incandescent bulbs in a closed room for time $t$ (light and heat cannot escape the room). The room starts a temperature $T$ and ends at ...
tlengman's user avatar
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Neutron double differential capture cross section

Can one define what is the double differential capture cross section for a neutron, and how one would construct an experiment to calculate the double differential cross section as a function of energy ...
MKF's user avatar
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1 answer
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Why only Lyman alpha transition suffer Redshift in the epoch of Recombination in Cosmology?

I was reading Baumann's book on cosmology (topic: Effective three level system). There it is said that in the epoch of recombination to form Hydrogen molecule two type of transition happens. $$ 2S \to ...
Kazi Abu Rousan's user avatar
1 vote
1 answer
103 views

450nm peak absorption [closed]

I am looking for an oxide compound (metal oxide, or similar preferably inorganic) which shows light peak absorption at 450 nm. I have troubles in finding the right compound, as most of the oxides have ...
Francesco's user avatar
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Absorbance spectrum of common metal oxides

I am looking into metal oxides particles, and I wonder where can I find the absorbance spectrum of visible light of common avaiable metal oxides?
Francesco's user avatar
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What is the influence of humidity on NDIR $\rm CO_2$ measurements?

The Question I would like to use an NDIR $\rm CO_2$ sensor to measure $\rm CO_2$ in the 0.1-3% range. However, in the course of my experiments, humidity may vary from ambient (50-60%) up to nearly 100%...
mranvick's user avatar
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Why we typically see no deeper into an atmosphere for an optical depth of 1?

In An Introduction to Modern Astrophysics (p.243), Carroll and Ostlie say that for a optical depth $\tau = 1$ the intensity will decline by a faction of $e^{-1}$. $I_\lambda = I_{\lambda,0}e^{-\tau}$ ...
BlurryConception's user avatar
1 vote
1 answer
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Refractive index of titanium dioxide films as a function of wavelength for 400 C ° annealed films

I used UV-Vis/NIR spectrophotometer to extract the measurements of refractive index %R corresponding with wavelengths in the range of 190-1100 nm of TiO2 thin film deposited on FTO glass substrate. ...
Mona's user avatar
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1 answer
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Formation of emission lines, absorption spectra

If we spectroscopically observe a cloud of hot gas, which is on the whole not very absorbent, and which is not illuminated by a source behind it, we observe emission lines. How does this type of ...
Bml's user avatar
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Convolution or addition? Proper way to model overlapping absorption line profiles

Suppose you obtain a measured spectral line shape (let's call it 'envelope') which appears as a skewed/asymmetric voigt profile. You know physically that the envelope line profile has this skew ...
kl_physicist's user avatar
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What effect, if any, does dissipative absorption have on aurora borealis? Why don't we see more colors as a result?

According to wikipedia, the aurora borealis is primarily caused by charged particles from the solar wind being redirected to the poles by earth's magnetic field and slamming into the nitrogen and ...
Robotic_Cow's user avatar
2 votes
0 answers
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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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Determination of absorption and scattering coefficients, given only the attenuation length

I'm attempting to write a Monte Carlo solution to the radiative transport equation in a highly anisotropic medium with known attenuation length $\lambda$. Due to limitations in our ability to measure ...
10GeV's user avatar
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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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Why do the 'colors' of liquids in differently sized glass cylinders appear similar despite varying absorption rates?

For some liquids, such as cooking oil, I have observed that when filling two glass cylinders (with lids) of different diameters (e.g., one with a 5 cm diameter and another with a 10 cm diameter) with ...
user1420303's user avatar
1 vote
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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
2 votes
0 answers
55 views

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 ...
Nadka's user avatar
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0 answers
23 views

Water vapor: refractive index and extinction coefficient ($n$ and $k$)

Looking for optical properties of water vapor (index of refraction and extinction coefficient) as a function of wavelength.
Iris's user avatar
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32 views

Absorption line of nitrogen at 337 nm

Nitrogen laser emits a laser at 337 nm. So, I think nitrogen has a laser absorption spectrum at 337 nm, but I have not found any information such as absorption coefficients around this wavelength from ...
X Guo's user avatar
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1 vote
2 answers
377 views

If photons are massless, how are they reflected and blocked by something that has mass? Shouldn't they pass right through any object?

If photons are massless, how do they get reflected, blocked when something comes in its way? Shouldn't the particle just pass right through any object?
Shristeerupa's user avatar
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12 views

Expansion and visibility of particles because of diffusion

A cloud forms as a point source containing a fixed quantity of particles and then expands according to the diffusion equation. Let's analyze how the visible size of the cloud changes with time. When ...
Edward Henry Brenner's user avatar
2 votes
1 answer
61 views

Influence of absorption, reflectance and light source on interference in thin films

I am not a physicist, but reading up on interference in thin films. I understood how the relation of two interfering light waves intensities $I_1$ and $I_2$ of a thin film (the first reflected at the ...
Iridium's user avatar
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24 votes
4 answers
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Why can't sunlight reach the very deep parts of an ocean?

Sunlight reaches the surface of the ocean and refracts. So it is still there. And its speed is about $225000$ km/s in water which is still incredibly fast. Light is a massless electromagnetic wave. So ...
Snack Exchange's user avatar
2 votes
1 answer
150 views

Why is UV radiation below 200nm strongly absorbed by Oxygen?

According to https://en.wikipedia.org/wiki/Ultraviolet#Subtypes Ultraviolet radiation below $200$ nm is considered to be Vacuum Ultraviolet, due to being strongly absorbed by atmospheric Oxygen. ...
blademan9999's user avatar
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Rotating wave approximation and linear response function

Is it true that the rotating wave approximation (RWA) is only the thing for the non-linear cases, and in the linear regime it does give any benefits? Let us say we have a rotating wave, so we don't ...
freude's user avatar
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1 answer
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How do degenerate states affect molecular absorption?

Molecular absorption of light is related to the transition dipole moment according to the equation from Hilborn, 1982: $$\sigma(\omega)=\frac{\pi \omega}{3\epsilon_0\hbar c} \frac{g_2}{g_1}\mu^2\rho(\...
ChaSta's user avatar
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1 vote
0 answers
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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
1 answer
234 views

When an electron absorbs a photon and gets excited to higher energy level what does happen to its kinetic and potential energy?

We know for a fact that if an electron absorbs a photon with enough energy it gets excited to a higher energy level, which increases that electron's total energy and we know that energy can present ...
medical physics's user avatar
0 votes
1 answer
38 views

Do vibrational frequencies produced from sound pass through your entire body? from one side to another? [closed]

when there is a noise by me, i feel the vibration on my skin from the direction it’s coming, it moves into my body. a wall of what sound would feel like passing through me. i perceive it as container ...
na.arah's user avatar
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0 answers
16 views

What 3d shape does water form when dropped on paper?

Say you have a stack of paper and you gently drop water on it (anything from 1 to 10 drops). How will water transfer through the paper ? What shape will it form ? What mathematical function best ...
Samuel Fyckes's user avatar
0 votes
1 answer
56 views

Heating of a metallic 'gray body' by radiation

I am interested in a realistic model for calculating the heating of a metallic body by solar radiation. Assumption (0) is vacuum, so neither conduction nor convection. Assumption (1) is integration ...
TomS's user avatar
  • 895
1 vote
1 answer
860 views

Absorption Spectra of Atmospheric Gases

From this previous Stackexchange question: Is a detailed absorption spectrum available for carbon dioxide from 300-1100nm? and this paper: https://www.osti.gov/servlets/purl/1613653 as well as this ...
G. Putnam's user avatar
  • 113
2 votes
2 answers
219 views

Why does light either get reflected, absorbed, or passes through a surface or obstacle?

For each of these 3 cases, I'm having trouble understanding... If light is reflected, does that mean that there was not sufficient energy by the photons to excite the electrons of the surface to ...
imagineerThat's user avatar
1 vote
1 answer
344 views

How does light interact with atoms? [closed]

I've read this answer regarding the difference between mere reflection and absorption followed by emission and I am struggling to understand some concepts. To begin with, we have some matter-light ...
Marvin's user avatar
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3 votes
3 answers
336 views

Why does sound absorbing foam stop echoes, but not transmission through the wall?

I understand echoes are sound reflections. But if foam absorbs sound, and if it reflects off the wall, then that means the waves travel through the foam, and if sound waves get transmitted from a ...
John Smith's user avatar
1 vote
3 answers
103 views

What is the explanation that the same material could receives and reflects EM wave signal while another absorbs?

Here is B-2 Spirit, a stealth bomber by Northrop Grumman. Another one is a depiction of a parabolic dish antenna receiver. As we knew, the B-2 is a stealth aircraft, which is not reflects the received ...
AirCraft Lover's user avatar

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