Questions tagged [absorption]

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

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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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1answer
144 views

Is there a zone where 'colour' overlaps between double rainbows?

Someone on social media posted this question based on a conversation with their (very cluey and creative) kid. Is there a zone between double rainbows where the 'colour' overlaps? This would be in ...
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Why don't absorption and emission lines cancel out in our Sun?

I was looking at this answer on why absorption lines and emission lines don't cancel out: An experiment shining light on the material and looking at the reflected spectrum will see absorption ...
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Light Inside a Spherical Droplet

Suppose that a monochromatic light beam of wavelength $\lambda$ bounces around inside a perfectly spherical droplet of glycerol (radius $r$, refractive index $n$, density $\rho$, molar mass $M$) ...
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1answer
526 views

Observed wavelength of moving distant star (Doppler shift) with hydrogen cloud absorption [closed]

A star is moving away from a stationary observer with known velocity $V_* = 3 \cdot 10^5 m/s$. Between the star and observer, there is a moving hydrogen gas cloud, which is approaching the stationary ...
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2answers
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Absorbtion of photon

Electrons in an atom absorbs an incoming Photon to gain energy and jump to a higher energy level (shell or different orbital) considering the fact that the photon doesn't have enough energy to make ...
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2answers
863 views

How to see wind?

Is there a wavelength of light at which you could see air moving? I was thinking it would be amazing to put on a pair of goggles which enables you to see how air moves around across a landscape, while ...
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3answers
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Why does a blackboard dry very quickly?

When you have made some stupid mistakes on a blackboard, you quickly want to erase it with a wet sponge before anyone sees them. So you clean the blackboard and within a minute the blackboard is clean ...
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2answers
163 views

Can any element absorb neutron in low energy?

I read somewhere that neutron can be absorbed by any element if we provide sufficient energy to the neutron and the element. I want to ask that if we have an energy spectrum of 1Gev/c and 10Gev/c and ...
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1answer
666 views

How do surfaces absorb or reflect light? Specifically, what is the physical process happening at the molecular level? [duplicate]

As an example, I know a leaf looks green because it absorbs red and blue light, but reflects green light*. My question is how the red and blue light are absorbed, not reflected. And conversely why the ...
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1answer
759 views

A question on the emission spectrum and absorption spectrum

I am submitting this question because I am confused on how light is absorbed and emitted from atoms and how that relates to the colours we see. I have tried reaseaching the answer to my question but ...
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What “happens” to the energy of a photon after it is absorbed?

The simple model of the colour of reflected light from objects (yes, colour perception is a function of the eye/brain) as I understand it is: Firstly I will write what I understand happens - which ...
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Why does it take time for absorption to set in?

I read this sentence in Optics Principles and Applications by Sharma regarding light dispersion: But since it takes some time for the absorption to set in, the trailing edge of the pulse is ...
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3answers
139 views

How does an electron know which is the next energy level?

Electrons absorb photons and jump to higher energy levels or excited states (or a higher energy orbit). They absorb only those photons which have energies equal to the energy gap between their current ...
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References for photo-absorption on a nucleus

I have spent lots of time looking for at least one good reference for nuclear photo-absorption, but it seems like most of the authors I ran into prefer not to make fundamental references. Does anybody ...
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1answer
980 views

Optimal laser wavelength for heating air

Lets say I want to heat air with laser,what wavelenght should I chose,ultraviolet,infrared or something in visible spectrum? To clarify,I want the laser beam to lose power and get converted to heat in ...
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1answer
302 views

How much air would be needed to block sunlight?

Was watching a sunset on the sea, I was wondering what would be a lower bound for the thickness of air needed to almost completely obscure the reddish light of the sun, or at least to make it ...
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1answer
155 views

Absorption of light in a medium with non-uniform optical density

I want to understand how exactly is the optical absorption signal obtained in the case of a medium with non-uniform optical density (OD). Do all volume elements along the direction of light ...
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2answers
404 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 ...
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1answer
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Are absorbed photons sinusoidal or sharp?

Probably this has an obvious answer but I did not manage to find it... When a photon of the appropriate frequency excites an atom, causing an electron transition, it acts as a “driving force”. In ...
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What is 'stimulated inhibition'?

I have heard that the equivalent to 'stimulated emission' (which occurs with bosons) for fermions is something called 'stimulated inhibition'. Please can someone explain what this processes is, and ...
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1answer
893 views

Absorption spectrum nitrogen

After a couple of hours of searching I cant find the absorpion spectrum of nitrogen in UV-Vis range (350-450 nm is what im looking for). Could anybody be so nice as to help me out? To specify I'm ...
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1answer
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Why does an positive absorbtion coefficient imply impossibility of population inversion?

In "Radiative Processes in Astrophysics" from Rybicki and Lightman there is a chapter called "6.9 The impossibility of a synchrotron maser in vacuum": They prove that there can not be a synchrotron ...
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Photon scattering and absorption in solution

I have a situation where I have an organic dye in aqueous solution, through which I have sent a (green) laser beam and measured the intensity. Compared to pure water, this solution showed much greater ...
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Where does the energy go in Vantablack?

Saw this article come by on Facebook the other day from I Fucking Love Science. It has a video of someone demoing what happens when you shine a laser on a piece of ...
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1answer
744 views

Why can't infrared rays go through the atmosphere?

Why can't infrared rays reach the earth? Why can't they pass through the atmosphere?
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1answer
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Few questions about the physical basis of metals colours?

I have a few questions about physical origins of metals colours: 1. What determines the colour of the metal (eg. yellow gold, rust-red copper and silvery colour of most metals)? I read on Wikipedia ...
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Shouldn't sound travel better through doors?

Sound travels much faster in solids than liquids and gases. Then why do we hear a fainter sound from the other room if we close the door than open it? As sound travels faster through solids......
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Emissivity of transparent window

I've been reading this article where the IR radiance of an IR-window ($MgF_2$, 1.75mm thick, passband 3-5$\mu m$) is calculated. At some point during the calculation they mention in a footnote: The ...
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1answer
837 views

Why can X-rays pass through a human body unimpeded yet optical waves don't as they get scattered and absorbed?

Why is it that optical waves get scattered or absorbed when directed into a human body yet X-rays pass straight through the body? The only difference between them is X-rays have a smaller wavelength ...
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1answer
32 views

Acoustic decoupling of small mechanical resonator

I am trying to lock and optical cavity mounted on a small aluminium breadboard. I notice when locking that any sound, even quiet whispering seems to disturb the process, causing a 100hz fluctuation to ...
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1answer
304 views

Difference between reflection and re émission of light [duplicate]

I would like to understand the difference between reflection of light and re emission. Indeed in both case an observer far from the object will se an electromagnetic field coming to him. When we ...
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Photoelectric effect absorption coefficient decreases with energy, why?

Consider the diagram below: (Author: Joshua Hykes source: Wikipedia) From this diagram we can see that the absorption coefficient for the photoelectric effect generically decreases with the increase ...
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1answer
131 views

What happens to the visible light that a substance does not reflect on an atomic level?

Let's say we have a blue, opaque material. If white light was incident on that material, the blue light would be absorbed by electrons and the electrons would transition to a higher energy state, and ...
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1answer
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What is absorption rate of WiFi and Bluetooth RF in water? [closed]

Specifically, frequencies 5.75GHz and 2.4-2.485GHz. I want to place a hermetically sealed circuit at the bottom of a gold fish bowl, and want to know if the water will significantly attenuate WiFi or ...
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1answer
390 views

Cardboard allows AM/FM waves but NOT light - Why?

I am going through Electromagnetic waves. In footnote, the author was giving illustration on transparency of materials. Was going through some references here as well as in Google. Many people ...
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1answer
518 views

Feynman diagram for photon absorption

What is the simplest Feynman diagram for photon absorption by an atom? Is it described by an incoming photon and bound atomic electron interacting at one vertex with an outgoing virtual electron ...
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1answer
215 views

Standard green glass reflection and absorption rates by wavelength [duplicate]

Is there any exact data on reflection and absorption rates based on wavelength for the common green glass materials ? I know the rate itself is dependent of the angle, the exact composition of the ...
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92 views

Why haven't we created a material that is completely invisible to the human eye? [closed]

From what I understand, If something was not reflecting photons in any direction, you could then see through it. If photons transfer into thermal energy could something very cold help? Could the ...
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Clarification regarding atmospheric opacity

I have taken a look at the related questions Can someone explain to me the concept of atmosphere opacity? and Why can spacecraft observe terrestrial gamma rays, but terrestrial observers not ...
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Why do you only hear the bass when someone nearby is wearing earphones?

When someone nearby is listening to music through earphones or headphones, usually you can only hear the bass (unless it's really loud where you can hear the singer's voice and the other instruments ...
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1answer
120 views

Is there a connection between the frequency of a photon and the oscillation frequency of the atom which absorbs it?

If a photon has energy $E$, we know it has angular frequency $\frac{E}{\hbar}$. If an atom has an energy gap $E$ between its ground and first excited state, we know that if the atom is in a ...
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Absorption spectra of molecules library

Do you know where I can find a library with absorption spectra? I would like it if then I could input a wavelength and get back a specific value. More specifically I would like to see the absorption ...
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Different width of spectral lines for different groups of stars

As seen in an HR-diagram, a certain stellar classification can correspond to more than one group/sequence of stars (G5 could for instance be either a giant, main sequence star or a white dwarf and so ...
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Why can't electrons absorb any energy (i.e. absorb some energy of the photons necessary and emit the residual)?

Recently I had a question in mind about the absorption of photons. Why is it that only specific energy levels can be absorbed by electrons? I mean, I get the idea that electrons in an atom have only ...
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How do Black Bodies Absorb and Emit Radiation? [duplicate]

I have learnt how the gases of elements are able to absorb only certain wavelengths of EM radiation corresponding to the energy transitions between energy levels of orbitals. Furthermore, these ...
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1answer
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Photon absorption in a medium - basic principle?

I am trying to understand the basic physics of photon absorption in a medium. Take the example of oxygenated hemoglobin (red curve). Clearly at different frequencies/energies relatively more or less ...
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Why do X-rays go through things?

I always heard that the smaller the wavelength, the more interactions take place. The sky is blue because the blue light scatters. So why is this not true for X-rays, which go through objects so ...
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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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What is the difference between a white object and a mirror in terms of heat absorption?

Will a white object be cooler than a mirror when exposed to direct sunlight? Or will it be the other way around? If mirrors bounce all visible light and some of the other elements of electromagnetic ...