Emission Definition and 567 Threads

Homework Statement C14 disintegrates by b-emission with a reaction energy (q value) of 0.155 MeV. A b-particles with an energy of 0.025MeV is emitted in a direction at 135° to the direction of motion of the recoil nucleus. Then the momenta of the three particles (b = V, 14N) involved in this...

Hi! I would like to wrap my head around a relatively simple issue. Lets say that you have an excited atom, which rests in your refernce frame. When it emits light, the atom will have a backreaction, and it will "gain momentum" with the opposite direction as the photon. Of course, without...

I'm reading Eisberg's Modern Physics and in it, in the atomic spectra chapter, he says: "We have been discussing the emission spectrum of an atom. A closely related property is the absorption spectrum. This may be measured with apparatus similar to that shown in figure (5-1) except that a...

Hi, if I read the article (see link) I get confused: Is it emission or reflection? If it is emission, how is it possible that the photons are emitted to one side? (Unfortenately I do not have access to the original article.)...

I can't get my head around stimulated emission.Why does a photon traveling towards an atom stimulate emission? The best way I could answer is that a photon has an electro magnetic field and this causes an excited atom to oscillate.This induces an excited electrons to fall down an orbital. But...

Feynman tells us, "The probability that an atom will emit a photon into a particular final state is increased by the factor (n+1) if there are already n photons in that state." 4–4 Emission and absorption of photons, http://www.feynmanlectures.caltech.edu/III_04.html The 1 in (N+1) comes from...

Can anyone tell me what is proton emission equation after muon capture for heavy nuclei?is it same with neutron emission equation??

I use an Olll filter to view emission nebula such as the Great Nebula in Orion. What is the mechanism by which Olll in such nebula emit photons of the wavelength that passes through my filter?

Homework Statement [/B] The top spectrum shows part of the Sun's spectrum. State and explain which letter best represents the light from a star that is similar to the Sun. Homework Equations None. The Attempt at a Solution I originally was thinking A but my book says B but only gives...

What's the interval between photons in stimulated emission? In stimulated emission one photon induces the emission of a second photon whose coherence length, energy, polarisation and direction of travel are all identical to its own. There must be a delay between the two photons, see below, so...

Homework Statement I am identifying equations on the final exam equation sheet for my quantum II class. I've identified them all except this one, what I am guessing is a transition rate for some kind of emission or absorption of radiation case. Please help me identify the physical situation...

I can just get the idea of a silvered surface reflecting IR and a black surface absorbing IR (analogous to how light behaves) but I can't see how a silvered surface, if warm is a poorer emitter than a Matt black surface, if warm? Would appreciate any help without going too in depth. Regards, G.

They say that substances have color because when light waves of all colors hit the substance, the atoms do absorb all the colors, except those that is its color. Red substance is red because it absorbs all the color waves, but reflects the red waves. But all the color waves the red substance...

Homework Statement The emission spectrum of an unknown element contains two lines - one in the visible portion of the spectrum, and the other, ultraviolet. Based on the following figure and what you have learned about Niels Bohr's model of the atom, account for the difference in energy between...

Hi, it is well known that spontaneous emission of an atom can be enhanced, if the atom sits at a node of the vacuum standing wave field in a cavity. My question is, why is it the node? At a node of a standing wave, there is zero intensity, so there should be no interaction between the atom and...

Hello, I have a short question: In relation to the Sun - is Black-body radiation ultimately the result of a combination of spontaneous (majority) and stimulated (minority) emission of photons? In relation to the IR emissions from everyday objects due to their temperature - is Black-body...

Ok, so I've got a practical report due tomorrow and I just wanted to clarify a few things. A bit of background knowledge first. The practical involved taking angular measurements for the emission lines of the Mercury spectrum using the apparatus, a spectrometer and a Mercury spectral tube...

Emission theories propose that the velocity of light depends on the velocity of the light source. But the ordinary Doppler effect assumes the velocity of light remains as ##c## with respect to the ether medium, even when the light source is moving at speed ##v## with respect to the ether. They...

How hot does a gas have to be to achieve its emission spectrum with a glass prism?

Homework Statement For our investigation, we used a diffraction grating spectrometer to observe the emission spectrum of mercury. We conducted the experiment in a pitch black room to avoid any unwanted light pollution, etc. Whilst conducting the experiment we observed a number of 'faint' lines...

I have heard of frustrated spontaneous emission that somehow says that an atom that normally emit light will cease to do so when its surroundings is incapable of absorbing light. How is this possible, and is this experimentally proven?

Two spaceships with their engines shut off and identical radio receiver-amplifier-reemitting devices are in the empty space, very far from each other and from any celestial body. The lag time from absorbing to reemitting in the device is vary small compared to the return time of the signal (2t)...

When two deuterons fuse, I understand they form an alpha particle in an excited state. Based on mass differences the fusion releases 23.85MeV, which is enough to eject a proton (19.81MeV) or a neutron (20.58MeV) from the alpha particle. It seems to prefer neutron emission, as this fusion is used...

Why are only certain colors of the emission spectrum in Hydrogen visible?

Science mag news article on a new electrical power plant being set-up by a start-up. It burns natural gas with pure oxygen and runs turbines with CO2. It makes water rather than using it and is in theory close to competitive economically. . Sounds good to me, but I'm no engineer.

Hi all, This is likely a naive question, following up on something @vanhees71 posted some time ago in another thread: My question is the following - if we take an electron that has, for example, absorbed a photon, is the portion of the wavefunction representing the electron in a lower energy...

I have some more detailed questions on this further on but I found it better to start with a very basic question first: If higher temperature is correlated with shorter emitting wavelengths, how come there are incandescent light bulbs that emit yellowish light but are hotter than incandescent...

I am now working on Thermal and Non-thermal light emission of materials, particular concerning the Planck law and Generalize Planck Law. I really want to understand the fundamental concept of this. So could you please suggest me some material, book on this subject? Thank you so much in advance,

Hi all, the title is probably a bit confusing but I was wondering. What determines the type of light emitted when electrons move down electron shells and emit energy? Why isn't all the light emitted the same colour?

Hey currently I am doing O levels and in my textbook I read that when a metallic wire (in CRO - the cathode) is heated up, it starts emitting its free electrons (thermionic emission). And also its a fact that electrons are responsible for electrical conductivity. A question just popped up in my...

Hi! Could someone explain to me why an electron at rest without any influence from a magnetic or electric field cannot emit a photon ? Could you explain it mathematically too ? Thanks in advance...

Why does the quantum dot's band gap increase as in shrinks in size? What is the principle behind this? Is the Heisenberg's uncertainty principle?

I’m looking for material capable to act as filament of thermionic emitter in open air. Classical tungsten filament is not capable, because it readily oxidizes. We experimented with filaments made from SiC and ZrO2 (Yttria stabilized). At 1900K SiC provides certain degree of emission, but it is...

The principle of operation of the laser is based on stimulated emission concept. In short, if a suitable energy photon hits the electron of an atom, in which the electron is in the excited state, there is a probability that the electron returns to the ground state. The photon emitted has the...

Hi everyone, I'm trying to understand why laser diodes need a stronger input current to start lasing when their temperature increases. If I tried to add thermal transitions to the rate equations governing the evolutions of an atom quantum level populations (let's say ##n_{up}## and...

My understanding is that once light or anything else crosses the event horizon, it will not re-emerge. However, we detect high energy beams of radiation coming from opposite sides of some of the celestial bodies that I have been told are types of black holes. Obviously I'm missing something here.

Hi all, I've been able to find the answers to most of my questions in these forums, but this time I was not able to. So here goes my first post: I've been learning about thin film interference, and it all makes sense to me except for the correlation between destructive interference caused by...

Hello A friend of mine asked me if he could improve the (amateur) characterization of minerals by studying the absorption spectra during the application of a magnetic field. I thought that maybe the electron cyclotron resonance could work, but then I noticed that very low temperatures are...

Hello, Ok, so I’ve been searching about this for a while and there seems to be a difference in explanations that confuses me. What concerns me is the exact detailed physical mechanism that makes particles cause a scatter of a photon and an emission of a photon. The Wiki page about scattering...

Hey, I kind of understand the process of the 21 cm emission of the atomic Hydrogen, I know how rare it should be but still it is detectable in our Galaxy due to the huge amount of atomic hydrogen it has. However, I was wondering if it is possible to detect the 21 cm emission line in a...

I'm reading Gerald Folland's "Quantum Field Theory: A Tourist Guide for Mathematicians" and I'm up to Section 6.2 which is called "A toy model for electrons in an atom". He has a nonrelativistic particle of mass M and a scalar field with quanta of mass m and the state space for the particle is...

Hi. In thermodynamic equilibrium, the ratio between spontaneous and stimulated emission is $$\frac{A_{21}\cdot N_2}{B_{21}\cdot N_2\cdot u(f)}=e^{\frac{hf}{k_B T}}-1$$ where ##A_{21}## and ##B_{21}## are Einstein coefficients. This means, that there's always much more spontaneous than...

To radiate energy, the Poynting vector must not drop faster than with the inverse square of the distance. Under what circumstances can EM angular momentum be emitted to the vacuum of space (i.e. without being recovered via inductive coupling) and yet not lead to energy losses through radiation...

It's been a while. But I have always received the help I needed on this forum. I had this question in my head, When a particle accelerates, it creates an oscillating electric field, and a photon. How much does this effect, affect the energy of the particle itself? Say I had a particle...

In Griffith and Sakurai QM book, spontaneous emission is treated as a closed system subject to time-dependent perturbation. Yet in quantum optics sponantanoues emission is treated as in the form master equation of density matrix. Even in two levels system where there is only one spontaneous...

Is there any inherent difference between amplified spontaneous emission and stimulated emission? Is not stimulated emission simply the mechanism by which ASE occurs? Is stimulated emission just a broader term? I've read the two terms in literature and just wanted to ensure I understood the...

If quantum dots are placed within the body, what is the excitation needed for us to observe its emission? X-rays? I have heard that Quantum dots are used in solar cells. How does the process work for the conversion of light to electricity? I also heard that Quantum dots can emit ultra violet...

Homework Statement A tube containing a isotope of radon, 22286Rn, is to be implanted in a patient. The radon has an initial activity of 1.6 * 104 Bq, a half-life of 4 days and it decays by alpha emission. To provide the correct dose, the tube, containing a freshly prepared sample of the...

I have read that magnesium’s flame is white, and the light emitted includes all the wavelengths of visible light. Calcium, on the other hand, needs less energy to excite its valence electron, and hence, during emission, the radiation given off has a longer wavelength (red light) and its flame is...

Homework Statement A student collects diffraction data using a lamp with known emission wavelengths of 425nm, 565nm, 600nm, and 700nm. These lines appeared on her spectroscope at 32mm, 59mm, 63mm, and 69mm(all measured from the same arbitrary 0mm position). With these data she is able to...