Questions tagged [absorption]

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

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88
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4answers
13k views

Why does a yellow object turn white under a yellow light? Shouldn't it turn yellow instead?

Recently I was eating a yellow rice for lunch in a restaurant with only yellow lights. But the rice looked white! I was intrigued by this because I always thought it should look yellow since the ...
48
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6answers
23k views

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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10answers
25k 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.
35
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3answers
5k views

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 ...
28
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2answers
5k 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 ...
27
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1answer
6k views

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 ...
22
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7answers
36k views

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 ...
19
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3answers
4k 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 ...
15
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4answers
2k views

Why do colours of object change due to incident light?

A leaf is green, a pen is blue and so on because those objects absorb all colours and reflect only one colour. However when red light is incident on these objects, their colour becomes reddish. Why is ...
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1answer
1k views

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 $\...
11
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3answers
845 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 ...
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2answers
3k 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's voice and the other instruments ...
9
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1answer
540 views

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......
8
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1answer
262 views

How does the atmospheric UVB attenuation of terrestrial planets compare?

On Earth, UVB (280nm - 315nm or 320nm depending on the source) undergoes extensive attenuation through the atmosphere, when observed at the planet's surface, as illustrated below: Image source This ...
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0answers
2k views

Understanding the virtual states referenced in multiphoton absorption studies

The Heisenberg energy-time uncertainty tells us that we can have so-called virtual states between eigenstates as long as the lifetime of these states is at most: $\tau = (\frac{h}{4 \pi E_v})$ Where ...
7
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3answers
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 ...
7
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1answer
916 views

Test whether a glass prevents you from getting your Vitamin D portion?

I work in an office with glass, which I believe filters the UV radiation of the sunlight. Is it possible to test if exposure to the light coming through the glass will supply Vitamin D for me as a ...
7
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3answers
523 views

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 ...
6
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1answer
320 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 ...
6
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2answers
3k views

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 ...
6
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1answer
146 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 ...
6
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1answer
202 views

Paint: “Darker When Dry”?

A great question I enjoy bringing up is why are things, in general, "darker when wet". This applies to porous and granular materials like wetted stone, paper, sand etc. It also comes up in painting ...
5
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1answer
688 views

How are problems in astronomical spectroscopy solved?

Astronomers based on the ground telescopes, watch the stars and make predictions about them based on the spectrum of light. But when the light from those stars reach the telescopes through the ...
5
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1answer
681 views

Why are UV protective eyeware Orange?

Many industrial processes use uv as a curing agent. When one uses such a process, one must protect one's eyes from the radiation. Most uv protective gear I have seen is tinted orange? Does this ...
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4answers
2k 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 ...
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3answers
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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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2answers
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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 ...
4
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3answers
737 views

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 ...
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3answers
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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 ...
4
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1answer
38 views

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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1answer
618 views

Absorption lines in the context of identifying elements in far away celestial objects

I understand that absorption lines are used to identify elements but how are individual absorption spectrums identified in the light that is received by a telescope?
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1answer
75 views

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. ...
4
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2answers
388 views

How exact does the wavelength of light have to be to be absorbed by an atom? [duplicate]

I have been reading sources such as this on absorption and emission which make statements such as: The interesting thing is that each atom will only absorb photons with exactly the right energy. ...
4
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1answer
765 views

Do higher frequency EM waves travel longer than lower EM frequency waves?

In radio communication, the distance traveling seems to be an important parameter before we choose the frequency band of communication. There is also a path-loss model that describes a distance $\...
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1answer
566 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 ...
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0answers
751 views

Absorption coefficient from HITEMP or HITRAN [closed]

How to calculate the absorption coefficient (for radiation) from HITEMP or HITRAN databases? Or where can I find some tables or plots for the absorption coefficient?
4
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1answer
80 views

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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4answers
3k 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, ...
3
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1answer
1k views

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 ...
3
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1answer
852 views

When an electron absorbs a photon doesn't that change it's mass?

When an electron absorbs a photon it leaps to a higher energy level, what exactly happens when an electron absorbs a photon? By the mass-energy equivalence doesn't that changes the electron's mass and ...
3
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2answers
747 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 ...
3
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2answers
139 views

Not-so-hot black shirt

As it is getting warmer here by the minute I was asking myself: Are there materials, that are black (in th visible range) but reflect (most) invisible light? Furthermore, I asked myself what ...
3
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2answers
988 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 ...
3
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4answers
554 views

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 ...
3
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1answer
115 views

Using the fine structure constant to measure atomic and molecular sizes

This is kind of a coursework question but it bring up some really interesting things about the fine structure constant $\alpha$ so I wanted to post it to not only make sure I understood something but ...
3
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1answer
21k views

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 ...
3
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1answer
766 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?
3
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1answer
2k views

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 ...
3
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1answer
223 views

Optical absorption in multilayer structure

Assume a hypothetical 3 media/ 1 layer structure with the following indices of refraction: $$n_1 = 2, n_2 = 2+i0.5, n_3 = 1$$ where the thickness of the layer is 100 nm and wavelength = 1000 nm. ...
3
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2answers
693 views

Photons and Absorption

Hello and thanks for reading my question: Imagine we send one photon at an atom, and it happens to be the right frequency such that it gets absorbed fully by an electron in this atom. Obviously that ...