Questions tagged [absorption]

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

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26 views

What is the difference between scattering and absorption/emission?

As far as I know, scattering occurs when light excites the atoms or molecules to their higher energy state(virtual state for scattering) followed by emitting photons corresponding to energy ...
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Power absorption - ferromagnetic resonance

Magnetic energy is given by: $$ E(t) = \mathbf{M}(t)\cdot \mathbf{H}(t)$$ Hence, the magnetic power becomes: $$P(t) = \mathbf{M}(t) \cdot \frac{\mathbf{H}(t)}{dt} + \mathbf{H}(t) \cdot \frac{\mathbf{...
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How can atmospheric CO2 absorption of infrared be 100% when its atmospheric concentration is 0.04%?

An absorption spectrum from high in the atmosphere of infrared radiation emitted from the earth, shows that for the 15µm wavelength there is almost complete absorption. This is attributed to ...
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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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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 ...
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227 views

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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A Problem about Line Broadening and Absorption coefficient

I am reading my textbook, Lasers by Anthony E. Siegman, and I just could not understand a point he made. In the chapter section about inhomogeneous broadening, he used a figure to show the transition ...
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393 views

What is the meaning of $\beta \gamma$ in 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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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 ...
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What car color absorbs the least heat from the Sun?

What color of a car absorbs the least amount of heat, when exposed to the Sun? I want to break this question into 3 sub questions : I know that white reflects all of the visible spectrum, but our Sun ...
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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 ...
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Nature of electromagnetic absorption by quantum and classical systems

Forgive me for lack of formality and possibly incorrect understanding, but hopefully someone can both help to explain the intuition and also add mathematical formalism. In classical electrodynamics, ...
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Can light travel through a maze? [closed]

I want to manufacture a light proof enclosure. I need to understand: if I design a cap with a "U" section profile edge and the body with "T" or "U" section profile edge, will light be able to get ...
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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 ...
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How black body absorbs light?

I learn that black body absorbs light, but couldn't get the mechanism behind it. I wish I could get help.
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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 ...
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646 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 ...
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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 ...
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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 ...
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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 ...
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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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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 ...
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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 ...
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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 ...
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417 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 ...
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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 ...
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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 ...
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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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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 ...
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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 ...
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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. ...
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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)^...
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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 ...
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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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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 $ ...