Emission Definition and 567 Threads

Hi guys, I am looking for a formula which I am sure exits but I cannot locate it. The problem is that a quantum dot absorbs a photon of wavelength λ0(dot is semiconductor or could be any other material). Assuming that it reemits a photon, what is the probability that this emitted photon will...

When you heat things up, they emit specific wavelengths of light, right? Like when you heat up sodium, it emits yellow. But don't things emit shorter wavelengths of light at higher temperatures? Like how hotter stars are blue and colder stars are yellow. Since stars are mostly hydrogen...

So, I was thinking about building a low power klystron (around 5W.) I know this involves making an electron gun and electron guns can emit x-rays. I have a few questions: 1. Will 5W produce x-rays? 2. If so, what is a safe dosage of x-rays? 3. How can I shield myself and others from the...

Hi Guys I´m studying the absorption and emission phenomena of a gas and, according to Kirchhoff "extended" law, for a body at thermodynamic equilibrium, the following statement is true. ελ(T,θ,φ) = Aλ(T, θ,φ). So, if i understood correctly the meaning of this equation, The amount of absorbed...

Usually Hawking radiation is treated from the point of view of an observer outside the black hole (by which I mean the event horizon, not the supposed singularity), in which case it is possible (although maybe not convenient) to treat the black hole as not having an interior. However, let us...

When i compare the thermal emission of two devices, should i apply same voltage (both draw different currents) or should I make sure the power is the same for both?

hi, i did an experiment of photoluminescence in the lab and i was wondering about the spectrum of emission. why we get emission of photons with energies below the energy gap of the semiconductor? thanks

Hello, For a given excitation energy, why a nucleus "choose" to evaporate preferentially a neutron or a proton? I mean, let us take for example the isotope 208Pb. Its neutron separation energy is 7367.87 keV while its proton separation energy is 8004 keV. If this isotope has an excitation energy...

Homework Statement The average wavelength that LED emits is 500nm. The electrical power of the LED is 300mW and the efficiency of turning energy into light is 66%. Number of emitted photons in unit time is? Homework Equations ##E_f=hcf## ##\frac{Pt}{E_f}=number of photons## The Attempt at a...

I'd like to know that apart from Gases coming out of tailpipe of a vehicle, how much is Solid particle mass exhausted per gallon of fuel? I tried to search but I couldn't get exact answer. e.g. After 1 gallon of fuel burnout, exhaust pipe emits 1 gm or 10 gm or 100 gm of solid particles (PM10...

Greetings, Is there a difference between reflection of radiation and emission after absorption? What causes this difference? Another related question: According to wikipedia: "Earth's surface and the clouds absorb visible and invisible radiation from the sun and re-emit much of the energy as...

Consider a piece of pure Fe hot enough to have a bright white color (about 2 000 ºC, e.g.) and the characteristic yellow narrow yellow emission of the Na atom. Does the Na yellow band will be present at the thermal spectra of the pure Fe? My guess: Yes.

Is it possible for an atom to emit a neutron or a proton?

In my education of QM, I've heard countless times how energy is quantized by Planck's Constant, and how radiation is only emitted and absorbed in these discrete steps. Recently I've heard that that's not the full picture of energy, and I was hoping you could draw some clarity for me. In...

Hey there folks! This is my first post so please be gentle... ;-) One of my students has been studying the emission spectrum of an acetylene flame. A gas mixture from both an acetylene cannister & an oxygen canister is fed out to a nozzle, a flame is ignited and we study the emission...

I am trying to calculate the Lyman-alpha wavelengths of photons emitted from different hydrogen-like atoms such as deuterium and positive helium ion 4He+, using the relation 1/λ = R*|1/ni^2 - 1/nf^2|, where R is the Rydberg constant and ni and nf are integer numbers corresponding to the initial...

A beam of electron in vacuum with velocity v enter a region of spa e with a electric field E. The field is such the electrons circle with radius r. The electrons are now accelerating at constant tangential speed. Because this is not an atomic orbital then by classical physics the electrons...

Homework Statement The Earth receives on average about 390 W m−2 of radiant thermal energy from the Sun, averaged over the whole of the Earth. It radiates an equal amount back into space, maintaining a thermal equilibrium that keeps the average temperature on Earth the same. Assuming the Earth...

klotza submitted a new PF Insights post The Basics of Positron Emission Tomography (PET) Continue reading the Original PF Insights Post.

In the never ending quest to understand a complicated idea for which I completely lack the academic requirements to do so, I'd like to ask a few basic questions that I hope will allow simple yes/no responses (to ease the frustration of the physicist/mathematician contributors). Sadly, the...

I’m curious, how can the energy from these waves ever be recovered? How can they be “received”? Is that in any way overlapping with “detected”? For EM, we have the time-reversed equivalent of emission just as often as we have the emission, but for these gravitational waves that would be absurd…...

I recently purchased some 660nm LEDs. They look kind of orange not deep red. What is the easiest and cheapest way to determine the emission spectrum. Eventually I wanted to try to use the 660nm LEDs to grow some plants.

Homework Statement A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is: Homework EquationsThe Attempt at a Solution I'm confused whether the half lives...

Hi, When a molecule makes a transition from high energy state to low energy state, it emits electromagnetic radiation with a certain wavelength, which can be collected as emission spectrum. However, I have a question right here: For any real case, there are quite a number of molecules in one...

My name is Nicholas Lee, and I am studying neuroscience, and I am trying to find a way to find better ways in neuroimaging, and microscopy to see the brain better, to find better cure for Parkinson's disease, and Alzheimer's, and epilepsy If you have a four inch cubic block of glass, and carbon...

I've read that H2O has an absorption/emission band around to 10 micron range. What conditions are required for photons of this wavelength to be emitted by H20 gas? In particular, how hot would the gas have to be? What amount of pressure is required? Under everyday conditions (like steam possible...

I got the explanation about stimulated emission and lasers as explained here: Understanding Stimulated Emission: Got the what, how about the why? What I'm still unsure about is if this also explains the simpler question of how light passes through a transparent medium, like glass, yet the...

In the emission theory of light, light waves can move at any speed. We can still apply the Doppler effect, but to the best of my knowledge, only the frequency changes, not the wavelength. The pattern for a diffraction grating only depends on the wavelength right? And we have observed...

.. reaction. This may seem a nonsensicle question but I'll go ahead anyway. Say if I have a process that has an emission spectra dominated by excited state molecular emission, can I relate this in any way to the amount / number of chemical reactions occurring? Thanks for any help

If there is continue emission of electrons from surface then what will be its effect on that surface? Some of my friends told me that there are billions billions electrons. Nothing happen. But i think there is also emission of billions of electrons within small time. Can this process make a...

I understand that the result of the hydrogen emission spectrum experiment was that only certain wavelengths of light were emitted and that led to the conclusion that electrons emit light when they relax and that they absorb light when they get excited. How does that prove that the energy for...

as described by einstein in his paper published a few days ago in 1917, photon emission can be spontaneous or stimulated. In stimulated emission, atoms can be in an 'excited' state and the passage of a photon through such a population can can cause the ejaculation of energy in the form of an...

I have just learned about the cathode ray tube in the class room. There is a part called electron gun in it which emits electrons and these electrons finally strike the fluorescent screen.(I hope its correct till here.) But I want to ask that won't there be a loss of electrons in this process...

Assuming that your surface temperature is 99.1 F and that you are an ideal blackbody radiator (you are close), find (a) the wavelength at which your spectral radiancy is maximum,(b) the power at which you emit thermal radiation in a wavelength range of 1.0 nm at that wavelength, from a surface...

Hi all, I have been getting the emission spectrum of a polymer for a while. The emission peak is very important for that polymer. How do I find the emission peak of the polymer? The reason I ask this question is that if I simply select the highest point, then several points at different...

Imagine that one has a single photon of 632nm. It enters the back end of an open-ended HeNe laser tube - one with no mirrors - and along its path, causes the emission of another photon. According to the wikipedia entry on stimulated emission (https://en.wikipedia.org/wiki/Stimulated_emission)...

Laser action by definition requires the presence of stimulated emission in the laser medium. The typical way of treating this semi-classically is to introduce the Einstein coefficients, in essentially an ad hoc way, then derive the Einstein equations for the various level population transitions...

Hi, I'm trying to find out why stimulated emission (creation of an identical photon) doesn't violate the no-cloning theorem. There are lots of different opinions on this on the internet, e.g. "the second photon is not exactly identical, the energy is slightly different" or "since stimulated...

How would someone go about to make a phased particle energy beam? What are the physics behind it? Any research that anyone knows on the subject that I could take a look at? Thanks

Hi all, Does anyone know where I can find data details of how Emission Spectra depends on temperature for the following materials: Single Hydrogen Molecular Hydrogen (H2) Helium That is, as I heat up each of the above materials by themselves, from room temperature to thousands of degrees, I'd...

From a book intro I've been reading, Scattering, Absorption and Emission of Light by Small Particles by Mishchenko, it states that when incident light hits a particle, that particle may absorb light, scatter light or emit the light. Excerpt: Can anyone explain to me, on a physical level, the...

So I realize that I'm probably wrong about this, but it seems to me that Hawking radiation cannot be emitted only at the event horizon. If we make the (albeit almost certainly wrong) assumption that the quantity of emitted particles is directly proportional to the potential for gravitational...

Hi, If I'm moving away from a light source flashing light, according to Doppler effect I would have more time between flashes from my perspective than a still observer from perspective of the source, my explanation would be that the source really waits this exact time, and I can relate it to a...

Looking for typical experimental parameters for measuring emission spectrum of both H and H2, specifically gas pressures. Also would like to know typical pressure range where spectrum transitions from H2 to H. Thanks.

I am using Renishaw confocal Raman microscope to do photoluminescence spectroscopy of some polymer inside microchannel. When I fix the laser power and exposure time, the absolute count of intensity will change from time to time even for the same sample. I was hoping the intensity should linearly...

What happens on the atomic level when light is reflected or refracted? Also why do some objects absorb light as heat?

I am using a Renishaw inVia confocal microscope to study emission spectrum of molecules. The excitation wavelength of laser that I use is 532nm. However, I met with a very basic problem. When I use the same material (say plain silicon), and use different objectives (20X, 50X, 100X), then I will...

Do photon emissions increase the gravity of the Sun by compressing it

Has electron recoil due to photon emission ever been confirmed by experiment? cause I can't find any reference to electron recoil being measured anywhere I look. If it has been measured, what methods do they use?

Is the Abraham-Lorentz force (Also called radiation reaction force) the only recoil experienced by an accelerating charge? Say an electron is accelerating downwards, and that a photon emitted from this electron travels right, perpendicular to the direction of motion of the electron. Does the...