# Questions tagged [absorption]

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

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0answers
6 views

### How would the earth's surface temperature change if the atmosphere was also opaque to light in the visible range?

In Andrew Dressler's 'introduction to modern climate change', a simplified model of the earth and its atmosphere is proposed to investigate the effect of atmospheric layers on the earth's surface ...
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### Dispersion of Light Passing Through Prism [on hold]

Why is light absorbed and reemitted when passing through a prism? How does this relate to dispersion due to a prism, in which higher frequencies are refracted at greater angles?
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### How do materials absorb light

I'm curious how light is absorbed in materials. From what I understand, when an electron absorbs a photon, it gets excited to an energy level that is higher than the level it's in and the energy ...
1answer
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### Layer of material that transmits light in one direction and absorbs it in the other direction

I am looking for a material (or layer of materials) which transmits light coming from one side and absorbs light coming from the other side. The absorption should be as good as possible and the ...
1answer
619 views

### Integrated absorption coefficient

The absorption coefficient is usually defined as $$\alpha(\nu)=\frac{1}{d}\ln\frac{I_0(\nu)}{I(\nu)},$$ where $d$ is the thickness of the sample, $\nu$ is the light frequency, and $I_0$ and $I$ are ...
1answer
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### Do dieletric mirrors and other reflective surfaces have a maximum intensity to which the absoprtion coefficient increases?

That is, if you shine a laser at a dielectric mirror so that the intensity(photons/seconds*cm^2)becomes sufficiently large, the scattering of the photons off the electrons in the surface atoms becomes ...
1answer
531 views

### 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 ...
1answer
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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 ...
1answer
220 views

### 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 ...
1answer
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### Why is absorbance calculated as $\log_{10}(1/R)$ and not $1-R$?

According to Lambert Beers law, the absorbance ($A$) of a sample at a given wavelength can be described in terms of its transmittance ($T$) according to: $A = \log_{10}(1/T)$ In near-infrared ...
2answers
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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 ...
1answer
139 views

### How much ionizing (carcinogenic) radiation is one exposed to on a commercial flight, what are the sources, and how could exposure be minimized? [closed]

I don't know if this is the best place to ask this question, but I figure a physics-based answer would be the most satisfying. I'd be happy to be convinced I'm being paranoid about protecting an ...
1answer
11 views

### What does “Metal based electronic transition” means?

Recently I've been reading on the chiroptical activity of metal nanoparticles protected by biomolecular ligands, which have optical activity signals that are manifested in the metal-based electronic ...
1answer
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### How to calculate the distance that 1-10 KeV x-rays have to travel in air to lose 90% of its energy?

I'm trying to calculate the distance of air that can strip a beam of 1-10 KeV x-rays from 90% of its original energy. I came across this graph which shows the mass attenuation coefficient of air, but ...
1answer
339 views

### 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 ...
2answers
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### What is absorbance and Transmittance?

I am currently doing some work in Spectroscopy, and I was wondering how are absorbance, and transmittance related? Do they have a domain, and range, how to read some sample graphs. I was ...
3answers
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### Radiation pressure and conservation of energy

TL;DR: How can radiation pressure conserve energy, if we consider the case where the atom absorbs all the Energy of the incident photon via its newly excited electron, and stills gains additional ...
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### Radius of rain drop on ground

Just an observation I made this monsoon, When a raindrop falls on the ground its colour starts to fade, this may be due to the absorption of water by the ground. But gradually the radius of the water ...
4answers
286 views

### 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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### 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 ...
3answers
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### How to describe the unit vector for a complex wave vector?

In optics, we often come across complex wave vectors that describe absorption, dispersion, etc. given as: $\textbf{k} = \textbf{k}_{real} + i\textbf{k}_{imag}$ The electric field in phasor notation ...
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### How sound absorption results in heat?

When sound passes through a medium (say, air) and hits the boundary atoms/molecules of another medium (say, a solid) ...... How would you continue the story ? What happens at the interface in cases ...
1answer
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### Light matter interaction (LASER) [closed]

I don't understand how a photon energy get absorbed or emitted by a electron. when photon incident on electron it absorbs photon energy and go to excited state, and when it come down it emits energy. ...
1answer
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### Why does the Complex Index of Refraction take part in the Reflection?

I'm aware that in Optics, the complex index-of-refraction $\eta = n+ik$ is used, which famously leads to the reflection property at an incident angle, i.e. Fresnel's law: R=\frac{(n-1)^2+k^2}{(n+1)^...
1answer
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### How does one obtain a semiconductor's absorption coefficient from first principles?

Is the absorption coefficient of a semiconducting material at a given wavelength obtainable from the material's band structure? If so, how? Are there any pedagogical papers you could recommend to help ...
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### Effect of anodisation dye colour on absorptivity-to-emissivity ratio of aluminium

Anodised aluminium is a common material used in space, and it is commonly dyed black as this gives it an absorptivity-to-emissivity (a/e) ratio close to unity. This page says black anodic films have ...
1answer
167 views

### Combining sound absorption coefficients

I am trying to predict the reverberation time in a room with different surfaces and different absorption coefficients (i.e. curtains, wood panels, carpet etc). My question is about how to calculate ...
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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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### Why do high altitudes have larger diurnal temperature variation than lower altitudes?

It seems like the lack of atmosphere should not be playing a role in the diurnal temperature variation because that's what makes it colder. Mountains are not that dry, usually.
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### Is it possible for a material to be transparent / opaque in the whole EM frequency spectrum

Water is (broadly) transparent to optical frequencies, but opaque in ultraviolet and mid-far infrared. (graph) Human flesh is (broadly) opaque in the optical frequencies, but transparent in the X-Ray ...
1answer
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### How do electrons ever receive the amount of energy needed to move up energy levels?

Suppose there is a (blackbody) electromagnetic radiation source. It should emit a finite amount of photons every second with an intensity against frequency graph looking similar to a Maxwell Boltzmann ...
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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 ...
2answers
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### Why do EM waves of millimetre wavelength not travel well through mediums?

So I'm an undergrad electrical engineer but I figured this would be a question more suited to physics. I'm working with high frequencies (30-300GHz) which correspond to EM waves of millimetre ...
2answers
418 views

### What is the linear attenuation coefficient and how does it relate to interaction probability?

I have misunderstanding the linear attenuation coefficient (L.A.C) concept. As known, L.A.C is depend on absorbed medium and energy of incident radiation. Supposing, L.A.C= 100 cm-1, how can this ...
1answer
368 views

### Bethe Bloch Plot

Why is the stopping power in Bethe Bloch-Plot shown against $\beta\gamma$ on the horizontal axis? Respectively what is the meaning of $\beta \gamma$? Plot taken from here
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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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### How does evaporator coil absorb heat when a cool liquid is passed inside it?

My question is how does evaporator coil inside a refrigerator cools the inside atmosphere by absorbing heat? I am fully confused, how the heat absorption happens? This technically sounds confusing.
1answer
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### Can gases be heated by absorbing laser light?

I have a narrow gas jet, with a laser pointed at it. I want to figure out whether the gas will absorb any thermal energy from the laser photons, if they are at a wavelength that the gas can absorb. ...
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### Black hole absorbing photons?

If a black hole has a radius that is not that much smaller than the wavelength of light emitted by the sun, and is at the same temperature, shouldn't it be able to absorb photons as well as emit them? ...
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### fluorescence wavelength limit

My understanding is that fluorescence occurs when light has sufficient energy to excite an electron, which then emits a different photon (always with a larger wavelength) and releases the energy it ...
1answer
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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 ...
1answer
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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.
1answer
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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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### 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 ...
3answers
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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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### 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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### 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 ...