Emission Definition and 571 Threads

Einstein coefficients tell us that there is some probability for an atom to go from E_1 to E_2 given by the coefficient of absorption. This is fine, but why is there only one coefficient (absorption) going from E_1 to E_2 and two for the transition E_2 to E_1? Spontaneous emission makes sense...

Like the title says: which factors play a role?Also, why do some (unstable) atoms emit alpha-particles, while others emit beta- or gamma-particles/radiation?Thanks for any insights!

The Rayleigh-Jeans- and Planck- radiation formulae are based on the assumption of standing waves in a cavity (seehttp://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html.) However, in nature one does not normally have any clearly defined cavity that would enable the development of standing waves...

i have a question about electron spin and photon spin.when an electron with 1/2 spin emits a photon with a 1 spin, does the electron change to have a -1/2 spin since it just lost 1 spin by emitting a photon? And does the same type of thing happen when an electron absorbs a photon? That would...

If a laser beam has a definite diagonal polarization, it is in a superposition of horizontal and vertical polarization. If that beam were then sent through another lasing medium and caused stimulated emission of another photon (or possibly several photons), would those be in superposition...

Imagine a Mach-Zehnder interferometer adjusted so that light comes out one face of the final beam splitter, as per normal use. In the arms, lasing material is added so that photons can cause stimulated emission of more photons that should be the same wavelength and in phase - they should be...

Why do we see more absorption lines in stellar spectra than emission lines?

in the inside of the material is heat also can transferred by radiation?

1. how do you block or interfere with the emf(electromagnetic field) emission generated by your brain? 2. how do you block or interfere with an EEG taken from the mind(what factor influence EEG taken from the mind and can add noise to the signal?). 3. Regarding US Patent 3,951,134 "Apparatus...

I've first method I tried was using f = v/λ to find the frequency, then E = hf to find the energy and then using E = (-13.6eV/n^2) - (-13.6eV/n^2) to rearrange and solve for the unknown n. However I got 5, the same as the original entry level. I also tried using 1/λ = R(1/4 - 1/n^2) to solve...

Ok, so I've been on a kick trying to really understand why QM and GR are incompatible. I think I get that GR can't be realistically converted into a quantum field because it creates some infinite series that you can't use the normal tricks you would for other QM fields. Hard block, ok got it...

Hi All In another thread I answered was a question related to this and noticed another as well, so I thought I would give the full answer in its own thread rather than write it out twice. The other question has been deleted but here is the full detail anyway. First see...

In ground state electron does not emit photon.Can we use QED to explain why in ground state electron does not emit any photons?

If you have a lump of the same species of radioactive isotopes, why can't the photons emitted from the radioactive decay of one nucleus cause spontaneous emission from other atoms? I presume it doesn't, because if it did, there would be a geometric effect of radioactive decay, which is not...

Hi i am trying to find the infrared emission spectrum of Lithium Nitrite on the web but having no luck. Has the spectrum been measured? If so, can I be redirected to the resource? This for general interest and a personal project. Thanks.

For t < 0 , all I can think of is a qualatative " the field is zero because the intensitity is 0 when the burst of light hasn't been emitted yet " For t >= 0 , I've tried squaring the given E and that let's me say the amplitudes are proportional (with a cos^2 term in the mix) But I feel like...

Hi All, When I teach the basic structure of a laser setup, stimulated emission appears as a fundamental phenomenon. But in no reference I found a description that could account for the increase of coherent length of the EM laser field. According to my knowledge, one photon typically doesn't...

Problem Statement: A sample of excited atoms lies 3.031×10^−19 J above the ground state. What is the emission wavelength of these atoms? Relevant Equations: E=hc/λ λ=hc/E I'm stuck on the first part. i.e; something / 3.031x10^-19J

I understand that a PET scan will produce Positrons which will come into contact with an electron and produce Gamma rays in the area where there is a high uptake of sugar (assume glucose). In this process of annihilating an electron, some poor atom will lose an electron which I assume would...

Our teacher taught us "Laser" today and it made me confused. So Electron s energy in n=1 is around 13 eV (-13eV) and in n=2 is around -3.4 eV. Our teacher told us if we radiate a photon which has 9.6 eV energy (the difference energy of the first and second layer, n1 and n2, which is 13-3.4=9.6...

Dear Sirs, Maybe this is general knowledge, but I couldn't find the answer where I looked, so please bear with me. Consider a circuit consisting of a mechanical generator (some spinning magnets and coils) and a wire across the generators output. At some point the wire gets hot and starts a...

Homework Statement U - 238 is undergoing alpha emission into Th - 234. U - 238 has half – life of 109 years. Calculate the emission rate of alpha when uranium has mass of 10 grams Homework Equations A = λN A = A0 (1/2)n , n = t / half - life The Attempt at a Solution Not sure how to do it but...

I understand the concept of stimulated emission and how it works as light amplification, but a certain technicality in its process eludes me. How is the inciting photon actually interacting with the electron that falls to a lower energy level? In every physical interaction that I know of there...

Homework Statement The diagram shows a circuit used for the investigation of photoelectric emission. The two electrodes E and F are made of different metals. The work function of electrode E is higher than that of electrode F. Which of the following graphs show the variation the current...

My question is about the speed of light. Our current understanding of light says that light is constant for all observers, and uses time dilation to explain this. Have we proven this? The speed of light emitted from a stationary object is equal to C. The speed of light emitted from a moving...

A radioactive source emits particles at an average rate of 1 pe second. Assume that the number of emissions follows a Poisson distribution. The emission rate changes such that the probability of 0 or 1 emission in 4 seconds becomes 0.8. What is the new rate? Thanks.

I didn't see where anyone else had brought this up. From the article: The telescopes are the Murchison Widefield Array (MWA) and the Australian Square Kilometre Array Pathfinder (ASKAP), and they were synchronized to observe the same patch of sky, searching that area for fast radio bursts...

Suppose you have a pair of electrons in the same quantum state, and are thus spin entangled, and they absorb a pair of photons and release them at the same time. How would this affect the photons? Would the photons be entangled? Would it affect the photon spin, and if so, how would it affect the...

I came across someone in the lighting industry who insists that because of Gauss's divergence theorem and Maxwell's Laws that when light is emitted from a surface that it is only emitted orthogonal to the surface. I have tried to point out numerous real world examples that contradict the...

Hey guys, new here. Here is my first question for the forums: Let's say that I have a controlled environment for an experiment whereby I want to heat, say, one cubic centimeter of steel until it is white hot. Assuming that I have perfect containment set up for it such that no energy can be...

Hey guys, I am looking for a database on gamma emission from the first few excited states of known isotopes for a piece of software we are putting together. Any format is fine. Thanks!

In my heat transfer course, I always had to do analysis of long-wavelength radiation between surfaces first, and find the heat radiated from one of the surface. Then, solar radiation is added to the problem, and suddenly it was said that solar radiation=heat radiated from this surface! Does...

I have seen people talking about measuring Doppler shift of stars to know how fast they are receding from us. But if I measured say a particular frequency f, how do I know whether this is shifted frequency or just the emission?

Please teach me: if stimulate photons have energy different from the difference of two energy levels of atom then what is happened?What is coefficent of the stimulate emission in this case?

Hi, I am trying to model the distribution of the light emission from a material when excited with neutrons in MCNP. I have been searching literature and found not many things. Could anyone provide me with sources from which I can get info? Thank you in advance.

I want to use small molecular - preferably CNT - "antennas" to produce THz signals to monitor activity in biological systems. After some googling, I've been reading things like "absorption spectra", "energy bands", "spectroscopy", as well as a bunch of antenna-science related jargon... I need...

Homework Statement We are investigating hydrogen in a plasma with the temperature 4500 ºC. Calculate the probability per atom and second for stimulated emission from 2p to 1s if the lifetime of 2p is 1.6 ns Homework Equations Planks radiation law: ##\rho (f) = \frac{8* \pi...

How does the emission cross section of an emitting atom (such as Yb atoms in glass) affect the laser performance, namely the slope efficiency (signal power vs absorbed pump power) and laser threshold? Thanks a lot

does anyone know what is the average angle of infrared emission is by a flat diamond surface or tha directional distrabution

Homework Statement We are investigating hydrogen in a plasma with the temperature 4500 ºC. Calculate the probability per atom and second for stimulated emission from 2p to 1s if the lifetime of 2p is 1.6 ns Homework Equations ##A=\frac{1}{\Sigma \tau}## $$A_{2,1} = \frac{8*\pi *h *...

What makes the core of some chromospheric lines such as the transition at 8542 A of the infrared Ca II triplet appear in emission in the dark umbra of sunspots?

Hi to everybody ! I was thinking about something which confuses me about wave emission. The question is simply the following: Does an electron emit light when it accelerate? or just during its deceleration? or maybe when acceleration and deceleration alternates in some order? I'm not really...

I’ve been curious about understanding the mechanism behind themionic emission from what I have read I found that themionic emission happen when the energy from added temperature excess the work function of the material. I also readed when temperature excesses 1000k themionic emission happens but...

Hi, Suppose I have a 1D material of length L, and I want to calculate the spontanious emission rate Γ at ressonance frequeny. From my understanding, when light passes in a material at ressonance frequency it gets absorved by an electron in the atom, and after a spontaneous emission time tspont...

Homework Statement For a black body all absorbed radiation is emitted. Kirchoff´s law states that at the same temperature T1 the emissivity and absorptivity of a surface are equal, which holds for nonblack bodies as well. So, what really differs a black body and a non-black body in this case?

Hello Everyone, I have some thoughts about Planck's law. The graph describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. I think the absorption (or absorbance?) spectrum of an ideal blackbody should be a horizontal...

Why more emission lines than absorption lines are usually observed in the atomic spectra of most elements hence explain why this occures?

I explain it better. If we bring an electron from higher to lower energy level, the energy gap will be emitted as electromagnetic wave, because of the conservation of energy. When the same situation applies for a physical body, for example letting if falling down from some height, what does it...

What is the difference between the photon interaction mechanisms in emission due to absorption and reflection?

Can Stimulated Emission in lasers be explained semi classically? If so, how?