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 does one account for the momentum of an absorbed photon?

Suppose I have an atom in its ground state $|g⟩$, and it has an excited state $|e⟩$ sitting at an energy $E_a=\hbar\omega_0$ above it. To excite the atom, one generally uses a photon of frequency $\...
Emilio Pisanty's user avatar
29 votes
1 answer
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How are photons "consumed"?

I have very little background in physics, so I apologize if this question is painfully naive. Consider the following thought experiment: an observer is in a closed room whose walls, floor, and ...
Adrian Petrescu's user avatar
14 votes
3 answers
2k views

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 ...
macco's user avatar
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Where do photons go when they are absorbed?

The answer I usually get (and I'm paraphrasing here) is that they disappear and are instead absorbed as heat energy. But I find it hard to believe that the photon simply "disappears." Common sense ...
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7 votes
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How precise must the energies match for absorption of photons?

According to Quantum Mechanics, in order for an atom to absorb a photon the energy of the photon must be precisely that of a "jump" between energy states of the atom. How precise must it be? If I ...
Tobias Tovedal's user avatar
4 votes
3 answers
4k views

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 ...
Quantum spaghettification's user avatar
50 votes
4 answers
5k views

How can an object absorb so many wavelengths, if their energies must match an energy level transition of an electron?

I believe I have a misunderstanding of some principles, but I have not, even through quite a bit of research, been able to understand this problem. My current understanding of transmission, ...
Ultralite's user avatar
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23 votes
7 answers
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Why do bass tones travel through walls?

I was in the shower while my roommate was listening to music and got to thinking about the fact that I could only hear the bass and lower drums through the walls. Why is this? The two possibilities I ...
Nick Van Hoogenstyn's user avatar
22 votes
3 answers
6k views

Why do lines in atomic spectra have thickness? (Bohr's Model)

Consider the atomic spectrum (absorption) of hydrogen. The Bohr's model postulates that there are only certain fixed orbits allowed in the atom. An atom will only be excited to a higher orbit, if it ...
Gerard's user avatar
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6 votes
3 answers
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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 ...
Nanoputian's user avatar
43 votes
10 answers
31k views

Why can't we see gases?

I am not sure what causes gas molecules to be invisible.This question may look silly but I really want to know the story behind it.
Praveen Kadambari's user avatar
3 votes
1 answer
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Is the Energy of an absorbed photon exactly the energy of the band gap?

I was wondering, if the Energy of a Photon which is absorbed by an Electron, hast to be exactly the Energy of the bound gap. So if i have two energy levels in an atom $E_2$ and $E_1$, does my ...
bobo's user avatar
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2 votes
1 answer
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Excitons - Increase in absorption

I have consulted a book by Mark Fox on Optical Properties of Solids, and it states: " The absorption of a photon by an inter-band transition in a semiconductor or insulator creates an electron in ...
Aleksejus Pacalovas's user avatar
29 votes
2 answers
6k views

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 ...
CognisMantis's user avatar
10 votes
2 answers
4k views

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 and the other instruments too). ...
hb20007's user avatar
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9 votes
4 answers
7k views

Can a photon be absorbed by a proton?

When incident light passes through a hydrogen gas, for example, does it have 50% chance (since it's a 1:1 ratio of protons to electrons) of getting absorbed by the proton? Any chance at all? If no, ...
Sparkler's user avatar
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4 votes
4 answers
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How can we prove that a photon is absorbed only once?

When I first heard about the photons and the double-slit experiment my immediate thought was the following: Alright, energy is not absorbed continuously but in discrete units, photons, but nature ...
Calmarius's user avatar
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4 votes
2 answers
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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 ...
theta's user avatar
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2 votes
2 answers
639 views

Why does the light instantly disappear when we switch off the source?

For example i take a box which is completely covered by the most perfect mirrors possible inside and inside that box i have a bulb whose bulb holder is also covered with the most perfect mirrors ...
Bhavesh's user avatar
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How can opaque black object occur?

I know the fact that a material appeared as black when all wavelength photons were absorbed. I also know that opaque object is the result of reflection and scattering of light wave. Is it right? ...
user47546's user avatar
0 votes
2 answers
607 views

Absorption spectrum of hydrogen atom

In absorption spectrum of hydrogen atom, only one electron is present in its one atom which is in ground state, so it means that all electrons can only absorb energy of photon of wavelength which lies ...
happy sharma's user avatar
34 votes
4 answers
6k views

Why is water a good neutron absorber?

I've seen this question asked multiple times, and the answer is never detailed. I initially assumed that either hydrogen or oxygen had relatively large neutron absorption cross sections, however that ...
ryani42's user avatar
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9 votes
3 answers
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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 ...
Clive Long's user avatar
8 votes
3 answers
7k views

How does radiation shielding using absorbing materials work?

I understand that, for example, a thick enough sheet of lead can absorb gamma radiation, but I want to understand what actually happens at the molecular/atomic/subatomic level. Also, can the same ...
Icarus's user avatar
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7 votes
2 answers
600 views

How can absorption spectra form if atoms can't remain in an excited state?

I have been tasked to write a research paper on stars. However, I know very little about physics in general. I am learning about how we can glean information about stars by analyzing the light that ...
Luke's user avatar
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6 votes
1 answer
314 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 ...
Errol Hunt's user avatar
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6 votes
4 answers
5k views

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 ...
Rab's user avatar
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4 votes
1 answer
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Frequency dependance of sound wave reflection

Why are high frequencies reflected more than low frequencies off an 'acoustically hard' surface such as concrete? I basically understand that the amount of reflection is determined by the impedance ...
Jaryd Miles's user avatar
4 votes
2 answers
3k 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?...
Slarty's user avatar
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3 answers
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A question about atomic clocks

I have a rather simple question about atomic clocks. I have read that: Microwave radiation with a frequency of exactly 9.192.631.770 cycles per second causes the outermost electron of cesium-133 ...
Bardo's user avatar
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2 answers
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Light Absorption of a glass

I've the $n$ (refractive index of the glass sheet ) and $t$ (the thickness of the glass sheet) with this information, how can I find the amount light absorption of the glass sheet?
David 2000's user avatar
3 votes
2 answers
2k views

How to connect Rabi frequency with absorption intensity?

If a particle with non-degenerate spectrum starts in some eigenstate, and the frequency of the external EM field matches some transition frequency, then this would lead the particle to do periodic ...
Ruslan's user avatar
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3 votes
2 answers
1k views

Light-matter interaction and an object's appearance

I am taking a course in Computer Graphics, and the teacher said we could put materials in there main categories: mirror like glossy or specular diffuse He suggested that the law of reflection is ...
user18490's user avatar
  • 203
3 votes
1 answer
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Calculating force absorbed by compression of a material (i.e. rubber)

Say I was trying to design padding to absorb impacts using polymers or similar materials, such as rubber. I have a good understanding of any relevant physics, most likely, but I wouldn't know where to ...
TheEnvironmentalist's user avatar
3 votes
1 answer
3k 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 ...
G. Wesseling's user avatar
3 votes
3 answers
304 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
2 votes
2 answers
273 views

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.
Saugat Pokharel's user avatar
2 votes
1 answer
110 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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2 votes
2 answers
522 views

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 ...
user210956's user avatar
  • 1,258
1 vote
1 answer
451 views

Thermal radiation vs emission spectra of gases

I am a high school student and I am very confused in absorption and emission spectrum of gases, for e,g take hydrogen at room temperature for simplicity, so that we can talk in terms of Bohr's model ...
Arun Bhardwaj's user avatar
1 vote
0 answers
51 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 ...
Janko Bradvica's user avatar
1 vote
1 answer
171 views

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 ...
CatsLoveJazz's user avatar
1 vote
1 answer
887 views

Where does the momentum go when atom absorb a photon? [duplicate]

Imagine an electron around an atom absorbs a photon and becomes excited, it has now jumped to a higher orbital. At this point in time, where does the momentum of the photon goes?
user6760's user avatar
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1 vote
6 answers
3k views

Hypothetically, if there was a substance that could absorb all visible light and reflected none, how would it appear to the human eye?

Would said substance just be perceived as a "hole" in our vision, if it was capable of absorbing 100% of all light? Also on a side note, would the absorption of all light instead of only visible ...
Et Lux Tenebris's user avatar
1 vote
0 answers
316 views

Absorption Spectrum

I just learnt what absorption and emission spectrum are. And our teacher introduced us to what Quantum Dots are. And showed us their absorption and emission spectra. And they look something like this ...
user52825's user avatar
1 vote
1 answer
247 views

Why exactly does a material reflect/absorb/refract light? [duplicate]

What is the property of the molecules of the material that causes it to behave differently when it interacts with light. Is it the frequency of the material? I was thinking that the resonant ...
Swaroop Joshi's user avatar
1 vote
2 answers
8k views

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 ...
eidylon's user avatar
  • 451
1 vote
1 answer
17k views

Absorption cross section and absorption coefficient

What is the absorption cross section, how is it measured? How to convert it to the absorption coefficient (measured in cm$^{-1}$)?
jokersobak's user avatar
1 vote
1 answer
3k views

Does the energy required to increase a volume of water's temperature increase as that temperature increases?

Obviously in a simple, classroom style experiment the energy required to increase water temperature is a constant and thus wouldn't change, but what if we made the experiment just slightly more real ...
user56598's user avatar
1 vote
2 answers
847 views

If black is the best absorber and radiator, why does it get hot?

I can guess that it’s emission peaks at a higher temperature than white. So when a light is turned onto a black and white piece of paper, the initial condition is not at equilibrium. As black absorbs ...
aquagremlin's user avatar
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