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

learn more… | top users | synonyms

0
votes
0answers
40 views

Why do thuds occur?

thud (noun): a dull, heavy sound, such as that made by an object falling to the ground. thud(verb): move, fall, or strike something with a dull, heavy sound. I'm not doing neither in the ...
1
vote
2answers
85 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 ...
12
votes
3answers
1k 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 ...
0
votes
1answer
47 views

Light absorption according to “Beer-Lambert” law [closed]

Beer-Lambert equation tells us the measure of absorption of light when it enters to a liquid and comes out from the other side. But I have a question there: Suppose a glass that filled with water. ...
6
votes
1answer
797 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 ...
33
votes
6answers
4k 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 ...
1
vote
1answer
59 views

Spectral lines and QM

In the various presentations I've seen so far in atomic physics of series such as the Balmer series, the wavelength of each spectral line is definite - but in QM, free particles have no definite ...
1
vote
1answer
29 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 ...
0
votes
0answers
16 views

Absorption coefficient polystyrene at 28 kHz

For a physics school project I need to know the absorption coefficient of polystyrene at 28 kHz. I looked online for a while, but there doesn't seem to be any websites giving the value, and also most ...
0
votes
1answer
31 views

How long remains a boron control rod?

I was wondering today, how long boron control rods remains in a nuclear power plant? When a boron atom absorbs two neutrons, it becomes the unstable isotope boron-12 and and the boron nuclei starts ...
4
votes
1answer
58 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 ...
0
votes
0answers
17 views

Resonance Raman scattering vs. absorption

I cannot understand resonance Raman scattering. It happens when there is a photon with resonant energy which is the same condition for absorption. How does the molecule "decide" if the photon is ...
0
votes
0answers
36 views

Why do aromatic rings absorb in UV?

Why do aromatic rings absorb in UV? I think that the whole molecule absorb light which causes transition of an electron to another molecule orbital.
3
votes
4answers
245 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 ...
2
votes
1answer
48 views

Intensity of light wave penetrating soft tissue

I'm studying for a medical physics exam and I'm struggling with the following question: Calculate the fraction of energy which penetrates to a depth of 3cm in soft tissue for a beam of light at a ...
0
votes
2answers
68 views

Does a reflecting object move faster than one that does not reflect?

Suppose you have two objects with the same mass and shape, such as a ball, and the only difference between the two is that one reflects light and the other does not. Would one object's velocity be ...
4
votes
1answer
327 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 ...
0
votes
2answers
126 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 ...
0
votes
1answer
36 views

photon absorption and emission

I was reading a book (Sears Zemansky) about this subject but I didn't understand something of an example, and this is that according to me there should be a process of emission for each of absorption ...
0
votes
0answers
51 views

Optical density

My knowledge about optical density as a quantity is limited and I have several questions regarding it. I know that it is the optical density of a medium that determines the speed of light in a ...
0
votes
1answer
22 views

What should the cross-correlation of two signals look like if their difference is non-significant?

I have some signal data from my lab that I want to present but I want to be able to say whether the signals I have are significantly different or not. I thought I could use cross-correlation. I ...
0
votes
0answers
38 views

QED: what is the relationship between emission and absorbtion spectrums? (and why do plants absorb blue light and emit green light..)

I'm interested in this because of photosynthesis, but hte question is general. I'm looking for a QED explanation. A lot of the explanations talk about light shining on a plant getting aborbed, ...
1
vote
3answers
96 views

Do electrons in absorption spectra absorb photons with enough energy to release them from their parent atoms?

Absorption spectrum theory says that electrons in the atoms absorb only photons of certain frequencies, which causes the dark lines in an absorption spectra. However, I understand that electrons that ...
0
votes
0answers
25 views

how to find whether molecules will absorb radiation of a particular wavelength or not?

I am trying to understand vertical temperature profile of Earth's atmosphere. We know that different frequencies get absorbed by molecules at certain heights. I want to show this mathematically. For ...
1
vote
0answers
62 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 ...
2
votes
1answer
28 views

Absorbative polarisers

Absorbative polarisers are one way of getting linearly polarised light from an unpolarised beam. The key idea is that these materials are manufactured such that light can be absorbed in all ...
0
votes
2answers
176 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 ...
2
votes
0answers
56 views

Connection: Work on dipole <-> optical absorption

If I consider a two-level system with a ground and an excited state, I can compute the instantaneous rate at which work is being done on the dipole $\mu(t)$ by an electric field $E(t)$: $\dot{W} = ...
0
votes
1answer
201 views

Will porridge/rice absorb water faster without a lid on it? [closed]

I just wonder if my porridge would be ready any faster if I take the lid off my tupperware container.
3
votes
1answer
86 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. ...
1
vote
1answer
264 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 ...
3
votes
2answers
194 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 ...
1
vote
1answer
103 views

Why does absorption cause seismic pulses to increase in length over distance?

The specific question I'm trying to answer is "How does the progressive loss of higher frequencies in a propagating seismic pulse lead to an increase in pulse length?" I understand how the higher ...
7
votes
3answers
1k 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 ...
3
votes
2answers
98 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 ...
4
votes
1answer
89 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?
1
vote
1answer
2k 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$^{-1}$)?
3
votes
0answers
109 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?
1
vote
0answers
35 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 ...
0
votes
0answers
21 views

Interpretation of decay associated difference spetrum

We measured transient absorption spectra and we got $\Delta A(\lambda,t)=A(\lambda,t)-A(\lambda,0)$. If we use DAS (decay associated spectra) for interpretation, we assume that our data have this ...
0
votes
1answer
75 views

Absorption of waves in a plasma

Suppose a plasma has characteristic frequency $\omega_p$. Since $$n = \sqrt{\left(1-\frac{\omega_p^2}{\omega^2}\right)} $$ For $\omega<\omega_p$, the refractive index will be imaginary - which ...
0
votes
2answers
193 views

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? ...
2
votes
2answers
105 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 ...
0
votes
1answer
41 views

Wave frequencies and barrier width?

I know a fact that says a wave can go through barriers thinner than its length. This is why for example FM radio can be picked anywhere while antenna TV needs direct sight to the transmitter. Is this ...
3
votes
1answer
80 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 ...
0
votes
2answers
41 views

Light absorbs and Color [closed]

I'm curious about how the material absorb the light and reflect the light back as colors in a sense of Quantum Mechanics (Quantum Electro Dynamics) Does Hadron related to the absorbs of photon ? or ...
32
votes
9answers
8k 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.
0
votes
1answer
109 views

Why the crest of water absorb more light than the trough of water?

I have done my experiment using water ripple to study the behavior of waves. I know that the crest will absorb more light than the trough so that the image created on the white paper sheet appeared to ...
0
votes
1answer
136 views

Does sound absorption depends upon the amplitude of sound wave?

I can understand the mechanism of frequency dependant sound absorption by most materials but does the sound attenuation also depends upon the AMPLITUDE(sound pressure or rather loudness/sound ...
0
votes
1answer
170 views

Why isn't steam/cloud blue like liquid and solid water?

Most of us here are aware as I think that pure water has a natural quest to absorb visible red colour wavelength slightly due do which liquid water and sometimes even ice appears to have a blue colour ...