Radiation Definition and 1000 Threads

Plasmas can emit radiation based on the acceleration of charged particles (which we generally consider as continuous), but for un-ionized matter compounds, transitions are quantized and photons have particular energies. At room temperature, collisional excitations are typically dominant. But if...

A few weeks ago, there were reports of super high levels of radiation similar to what sweden found when chernobyl ejected core material. Were these reports in error or have they not yet found the source?

Hello, Let me first describe the situation I am thinking of: suppose we consider an object in the form of a square with some thickness (e.g. a mirror). Suppose further, that the gravitational force pulling the object towards the sun and the radiation pressure due to the sunlight are in balance...

Hi, Can someone please explain as to why light beams attract or repel each other even when they don't have charge. Seems like it behaves like two current carrying parallel wires. There is very little material about this which goes completely above the head. Thanks

Hawking radiation formula shows the fact that when charge and angular momentum increases in a Kerr-Newman black hole (angular momentum in Kerr black hole) Hawking radiation decreases. Can someone explain this? Thank you.

Homework Statement Homework EquationsThe Attempt at a Solution Using Stefan Boltzmann Law , The power emitted per unit area by the small sphere is P/A = eσT4 . The power absorbed per unit area by the surface is given as P/A = eσT04 . How should I use the distance between the two surfaces ?

Every objects emit thermal radiation. Now consider this case: Sun emits waves in a certian electromagneic spectrum (UV + thermal radiation + ecc...); glass is transparent to thermal radiation that usually reach Earth's surface. UV and other radiations are mainly absorbed by Ozone and other...

I'm curious to figure out if I'm operating a transmitter with safety compliance regarding its HERP (Hazards of Electromagnetic Radiation to Personnel). Put simply, the transmitter has a low and high output capability of 2w and 10w. The antenna it operates on has an 11db gain. Radiating around...

Bear with me, I am just a chemist. Observations took several days (up to two weeks if memory serves me well). What I wonder is - why had different types of the EM radiation came at different times? Gamma burst was observed at almost exactly the same time gravitational waves were detected, but...

first question From what i read Hawking radiation is a particle and ant particle created on the event horizon of a black hole, one particle is pulled into the black hole letting the other escape, why does the one outside of the event horizon escape instead of both being pulled in? It would still...

I have a sci-fi idea regarding being able to move planets around like billiard balls. I'm theorizing that, after a nova, some of the bands of material around a star formed a new ring of rocky planets around a Neutron Star. Naturally, these are bathed in radiation. Having never taken high...

I've been recently studying the correlated-k method of calculating the absorption of EM radiation when passing through a sample of given thickness. I'm not sure if anyone here has experience on the same subject, but in case there is I have some questions... Suppose I have a material sample that...

I took Stephan's law for thermal radiation and I have a couple of questions about it. 1) The law states that the full energy radiated in 1 sec is equal to c T^4 where c is 5.67*10^-8 and T in kelvins and In the book they said if it has surroundings then the net energy emitted would be q = c A...

Problem Description: I have a solar panel of some surface area, material, and thickness mounted to an enclosure. The panel is isolated from the enclosure at some distance with a multitude of materials (air, insulation, plastic, metal) between the back surface of the panel and interior volume...

Are there kinds of black hole radiation other than that proposed by Hawking? Note that I'm talking about truly black hole radiation, not radiation from matter that orbits the black hole, etc. How can we conciliate such phenomenon with General Relativity? I mean, this seems to completely...

So, if frequency(max) of light emitted from an object proportional to temperature in kelvin, how can sun have max frequency around the yellow region while blue flames are much less hot?

Hi All, Consider an elastic sphere which is homogeneously charged and suferring an harmonic inflation and deflation. Is it correct to explain the theoretical result that it does not emmit radiation, even though all of its charge elements are accelerating, as a systematic effect of destructive...

To my understanding, photons have no charge, so how does the magnetic field control them. Also side question - in the diagrams I see the photons seem to kind of curve around the magnetic field, does that mean they are accelerating?

In the radiation detection, it's of common use pulse-type systems, which have a preamplifier between the detector and the amplifier. I have read that the preamplifier primary function is reduction of attenuation of the signal that exits from the detector by matching the impedance of the detector...

Is it possible for a transition between two atomic states to proceed by emission of gravitational, rather than electromagnetic, radiation?

Hi everybody, How do you find the heat radiation between two surfaces that aren’t perfectly parallel or perpendicular to each other? I know that the view factors play a part, however, I can only dig up view factors for parallel and perpendicular surfaces...

I'm doing a little experiment on reducing iron oxide back to bare iron. I'm going to use a blued rod, coconut oil and ultraviolet light. Im using coconut oil because information from this site suggests that it is very transparent to uv light. https://www.hindawi.com/journals/jspec/2013/540417/...

I am trying to calculate how much a foil liner helps keep the inside of a package cool. I have calculated the rate of conduction but am now concerned with radiation. Above is the equation I am using. The emissivity for the material is 0.05, the area is 1 m^2, the outside air temp is 295...

I've been trying to read up and understand why a air burst of a nuclear weapon is less catastrophic than a ground burst when speaking about nuclear fallout. I think I understand that intensity of the dangerous radiation falls off quickly because of an inverse square law, but what happens to the...

Hello During a simulation of light in gamma-scintillator interaction, it seems that there are a lot of Cerenkov photons. I don't know their contribution to the final intensity (it will need a long time to compute it). The textbooks usually say that the gamma ray will produce secondary...

Homework Statement Can't model a simplfied version of my problem, it's a Steady State Thermal problem. I'm trying to get the superficial temperature of a copper tube and the heat transfer from a flame to the tube(this is a simplified version of the problem). Now my problem started when I...

I have some questions regarding the temperature of empty space in a de Sitter universe or to say it better - the Hawking radiation emmited from the cosmological horizon: 1) Do particles that make up the radiation get produced by the empty space inside the patch (the Bunch Davies vacuum) or by...

In a spectrum from an MCA (that is hooked up to a scintillator and PMT), does an increase in amplifier gain cause the peak to shift towards higher channels? I have a source and its really weak so while calibrating my detector, I had to turn the gain up way high to see a peak, but I'd preferably...

Homework Statement This isn't a homework question but something I'm working on that I thought should be simple. Two disks (area ##A## and thickness ##d##) are joined together and placed under a radiation heater in vacuum, so that one side of the top disk is heated with a constant power. Assume...

Is none detection evidence of no gravitational radiation?arXiv:1707.06755 [pdf, other] Reanalysis of the BICEP2, Keck and Planck Data: No Evidence for Gravitational Radiation J. Richard Gott III (Princeton University), Wesley N. Colley (University of Alabama in Huntsville) Comments: LaTeX (MNRAS...

Hi, this has been probably asked a few times here but let me do it again,Since I'm planning to go to Chernobyl NPP for a "hands on" dosimetry learning experience and also for some adventure, I was wondering how safe or should I rather say necessary it would be to go inside the plant itself...

I haven't though about this from such a perspective but today while reading wikipedia (yes yes not the best source) I got confused, now the "eV" is said to measure the energy gained by an electron between a potential difference of 1V. I assume particle physicists use this measurement because its...

Hi everyone! I've been reading about these topics (Feynman lectures and more on the internet and some books) but I still have a doubt, maybe because I haven't understood the whole of it. This is my doubt: Think of an imaginary situation in which we have an accelerating charge. The...

Hello all, I was driving down the road yesterday, and I realized that I don't really have a solid grasp on how frictional forces cause infrared radiation. Can anyone explain, or direct me to a resource that explains, how this happens at the atomic level? I am thinking that the work done...

I have come across the following multi-explanations of how Hawking radiation/evaporation of a black hole happens: Particle/anti-particle story: particle/antiparticle pair creation from vacuum near the event get torn apart - one going into black hole, the other away; in some of these...

Hello, the name's Mike and I'm a newbie here, I have a question pertaining to solar angles required to calculate a solar panel's hourly generation over one year. Total solar irradiance on a tilted surface equals the sum of the direct, diffuse and reflected component. In my case, reflection is...

A couple of points I need clarification on. Objects outside of the event horizon feel the pull of the black hole - so the closer the object is to the event horizon but still outside of it the more pull the object feels to be sucked into the event horizon? Is that the correct view? As far...

I am looking for bulbs that would be emitting a spectrum characterized by a color temperature of between 500K and 1000K or any kind of light fixture that only emits long IR wavelengths. Does such a thing exist?

Homework Statement What is the net heat flow of an aluminum disk (emissivity = 0.05) with radius 10 cm and temperature 293K placed inside a room where the temperature is 300K? Asurface = π*r2 = 0.01π m2 Homework Equations Hnet = A*e*σ(Tradiate4-Tabsorb4) The Attempt at a Solution By simply...

A bar of iron is 0.5m long, 0.2m wide and 0.1m high (which means its volume is 1.0 × 10−2m3 and its surface area is 3.4 × 10−1m2 ). Iron has a density of 7900 kg m3 , a heat capacity of 400 J kg◦C , and a coefficient of linear expansion of 1.2 × 10−5 . The bar of iron is initially at 600K...

A clump of charged particles moving in circular motion emits em radiation. But if I go on increasing no. of charged particles till the time the system becomes current in circular path, then since each particle is having same acceleration and velocity, the current will be uniform. So, now the...

Homework Statement Homework Equations Radiation pressure i.e.R.P is the instantaneous pressure exerted by radiation on a perfectly absorbing surface perpendicular to the propagation vector of the radiation. Maxwell has shown that R.P = u , (1) where u is energy density R.P = F/A, (2) F...

If dolphins thought the universe was just a really big ocean, and if they had come up with the theory of general relativity, how would the fact that certain particles radiate faster than light through water shape their version of the theory? Would it be essentially the same with the human...

Are quantum harmonic oscillators, vacuum fluctuations and radiation modes the same? Is vacuum energy caused by vacuum quantum fluctuations?

Hello! How can ordinary material become radioactive, if exposed to radioactive sources? I read that Marie Curie's notes are still radioactive and I am not sure I understand how. As far as I know gamma and X-rays can excite or ionize an atom or excite a nucleus. How does this make the radiated...

How do you account for the conservation of momentum for a photon? Specifically, if you have light traveling in a medium where the refractive index is not constant. For example, a graded index multi mode fiber optic. So here is another diagram to help articulate my question. Inside this graded...

hi guys i was just wondering if i can use one of those neon indicator as some sort of ionization champer or as a crude geiger-mullar tube. and use the basic circuit of the radiation detector to make a simple radiation detector/counter this is the circuit i came up with : so the circuit works...

Hi all, I've only just started studying nuclear physics so forgive me if this question makes no sense. I've read that the way neutron shielding works (in simple terms)is that the neutrons act as billiard balls by knocking into the shielding material atoms and being scattered like this until...

Homework Statement A satellite to reflect radar is a 3.5-m-diameter, 2.0-mm-thick spherical copper shell. While orbiting the earth, the satellite absorbs sunlight and is warmed to 50 °C. When it passes into the Earth's shadow, the satellite radiates energy to deep space. You can assume a...

Hello everyone! Maybe someone good at this topic or met this problem before, because I was really confused reading about this << Link deleted by Mentors as Spam >> Can someone tell me: does it actually work? And how terahertz radiation can influence on the human body, considering that THz waves...