Radiation Definition and 1000 Threads

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...

Homework Statement The Planck blackbody spectrum is given by u(ω,t)=\frac{ħω^3}{π^2c^3(e^{βħω}-1)} Show that the peak of the Planck spectrum for a blackbody at a temperature T occurs at the wavelength λ_{max}T=0.29 where T is in Kelvin and λmax is in cm. Homework Equations...

Guys I have little doubt and I want you to rectify that Am I wrong or right. I think anybody at room temp or any temp emits each and every type of radiation but intensity of radiation is less for high wavelength or low wavelength waves at room temp and intensity is good enough for visible light...

Antennas work with variable current that leads to accelerations and deceleration ofor the electrons, the frequency of the photon or the electromagnetic radiation I want to generate depends on the change in kinetic energy of the electron E= hf= change of kinetic energy of the electron, according...

Let`s say you have a "magnetic field" (call it B) and let`s say it has a z direction, all over the space. Now let's kick an electron into the scene perpendicular to z. It will feel a force F=e v B to the axis z. Given a velocity v = v0 this won't change. We have an electron running in a circle...

Hello, please, what would be the protecting clothes for raidation and how efective it really is?

Hello, I wish to ask, if a kind of nuclear attack would happen, what radiation would it be, how far and for how long? How can we know how the radioation amount would change with time? Many thanks!

Hi, recently this conversation came up with me and one of my friends talking about the nuclear tourists of these days which is becoming more and more part of urban exploration. Now I tried google but I mainly got results talking about the risk and effects of radiation exposure during birth and...

Can radiation be defined as mass transfer or hear transfer? Like alpha rays and cathode rays involve particles so they could be called as mass transfer and at the same time the transfer energy which is heat energy.

Hello! Is it possible to detect THz radiation (300 GHz - 1 THz) with conductor or dipole antenna used to detect radio waves? I know that THz radiation may be detected in spectroscopic set-ups with a photoconductive antenna based on the semiconductor. In this case, the light from laser create...

Does the nature of radiation emitted by dense bodies like black holes differ in frequency from radiation emitted by regular stars like our Sun ? I believe that the former radiates more x-rays and high frequencies rather than the latter which radiates mainly uv, visible and infrared ranges. Is...

Why does a steel ball appear hotter than a charcoal piece at the same temperature when picked up by bare hands?

Good morning all, I was just wondering the following question. When an electron is accelerated it emits electromagnetic radiation, depending on how much it is accelerated the energy varies so the frecuency does and the electromagnetic wave emitted would be of different colors or maybe even...

I've always read in my Physics textbooks that high energy EM waves like x-rays and gamma rays, if our body is exposed to them for a long time, can damage the skin significantly. However, how does that happen at an atomic level? As far as I'm concerned, the thing that differentiates a high...

It's mentioned in my book that blackbody radiation can verify the particle nature of electron could anyone explain this to me,please?

Hello Forum, Thermal energy (heat) is associated to the infrared portion of the electromagnetic spectrum. Why? I know the human body emits radiation in the infrared (10 micron). Heat is associated to warming. Are infrared wavelength the resonant wavelengths at which molecules in most objects...

As far as I know, in most of metals, IR radiation is reflected almost entirely and is not absorbed by metals. How does a metal become warmed under IR radiation? or does reflection, on its own, can warm up a metal?

In a smoke detector there is 1 muCi of Am-241. I'm assuming that means it emits (3.7x10^10)*(1x10^-6)=3.7x10^4 alpha particles per second. Each alpha particle has a charge of 2e, so it seems to me that this stream of particles leaving the Am-241 pellet would carry a current of...

Dear all, I needed help in finding a source where the derivation of radiation emitted by a dielectric body is laid out. The derivation of spectral density of radiation emitted from a blackbody at a temperature ##T## is given in many books by populating the energy states using Bose-Einstein...

In my Part I post https://www.physicsforums.com/threads/qs-re-hawking-radiation-part-i.873163/reply?quote=5482437 I asked if there were any errors in my summary description of the Hawking radiation phenomenon. So far none have been posted. In this thread I want to learn some additional facts...

I am reading Jackson's book on classical electrodynamics. It said in page 412 to 415 (3rd edition) that the total power radiated by a dipole is proportional to k^4 (equation 9.24) quadrupole is proportional to k^6 (equation 9.49) But why does the linear antenna at page 412, which is a dipole...

I am starting this thread to continue asking questions regarding the Hawking Radiation phenomenon which were discussed in the Comments thread about the Insights article “Misconceptions about Virtual Particles”. This discussion has been mostly a dialogue between A. Neumaier and myself starting...

I'm working on a lab and the task is to determine the half life of an element studying the beta radiation or the gamma radiation (emitted from the daughter). I have all the data and I'm done with the beta part, that was pretty straight forward. I have no clue how to relate the gamma radiation to...

The following question/thought experiment is based on the dual nature (particle/wave) of electromagnetic radiation. Consider the emisson of a single photon on a 3D grid along the x-axis with its origin at (0,0,0). The only matter in this experiment consists of “electrons” found only in...

Homework Statement When an instable atom emits alpha or beta particles. Doesn't the overal electrical charge of the remaining atom change? For example when an atom emits alpha decay, a helium core is emitted, this results in the lose of two protons (forthe radiating atom). But doens't this mean...

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...

A black hole evaporates through hawking radiation, what I don't get is the requirement for an energy-negative energy pair production. Since it's the black hole's gravitational energy that's responsible for the pair production, even if one of them escapes, the black hole would lose energy anyway...

So my question is, how long can you be exposed to a gamma radiation for? Specifically, I've been working with a sealed cobalt-60 source for a final presentation. Now my professor noted to me that these sources we're using aren't radioactive enough to cause us any harm. However, I've been...

Hi, I want to test this radiation detector http://www.teviso.com/en/products/radiation-sensor-rd3024.htm The problem is we don't have strong nuclear radiation sources or even weak ones , can i mimic the radiation ?? For example can i use Microwave sources or RF field or other radiation sources...

It is well known that a circular loop of steady current does not radiate, even though each individual charge is undergoing centripetal acceleration. How about a loop of steady current that is shaped in a square? Does this structure radiate?

Homework Statement Homework Equations E=100 kV/m E=cB B = E/c B=(100000/2.998*10^8) B=0.0003335557 m = 10g = 0.01kg A=0.5mm^2 = 5*10^-7 m^2 I = (EB)/(4п*10^-7) = (100000)(0.0003335557) / (4п*10^-7) I = 26543519.23 The Attempt at a Solution a) Pressure = I/c =...

Homework Statement Suppose you walk into a sauna that has an ambient temperature of 57.0°C. Calculate the rate of heat transfer to you by radiation given your skin temperature is 37.0°C, the emissivity of skin is 0.95, and the surface area of your body is 1.60 m2. I solved this first part and...

I was playing around with numbers and found that the equivalent temperature for Hawking radiation from a Planck mass black hole is ~5×1030 K. Later, I saw that the Hagedorn temperature for strings (where the partition function is expected to diverge) is reported to be around ~1030 K. I thought...

Hi all, I am new here, and want to thank you for help in advance! I am working on a project and need some help - I need to figure out surface temp on an object at some distance from the heat source: I need some help getting started. Is it going to be: Heat transfer (radiation) + Heat...

Forgive me for this stupid question, but how do I convert between and I tried c = νλ but that doesn't work. This is the Rayleigh Jeans Law by the way.

I just read that if we have an antenna, then if the radiation resistance in the antenna is small, then the antenna is an inefficient antenna? This seems somehow counter intuitive to me. Could anyone help explain?

Dear, I' looking for three books about radiation,listed below: (1) Alpha, Beta and Gamma Ray Spectroscopy, K. Siegbahn. There is a link to amazon.http://www.amazon.com/dp/072040083X/?tag=pfamazon01-20 (2)Beta- and gamma-ray spectroscopy, K. Siegbahn.There is a link to read online but...

So while watching Better Call Saul I asked myself, if you shielded yourself from radiation like Chuck, not only electromagnetic but all types as much as you could, say in your office, car, and home so most of your time is spent with significantly less tiny particles messing with your cells...

Dear PF Forum, I'm trying to make sense about Hawking radiation in Black Hole. And that leads me into entropy. I read this equation in https://en.wikipedia.org/wiki/Entropy What does that mean? S is the change of Entropy What does Qrev mean there? Is it in Calorie? then Joule? T, I think is in...

I have a few doubts regarding antenna radiation and propogation. Kindly look into it and clarify. Consider a Hertzian dipole antenna, DOUBT # 1. Generally, when the power is mentioned for an antenna elements such as the power dissipated across radiation resistance(Rrad) P radiated =...

my understanding of beta radiation is that an up quark in a proton changes to a down quark, forming a neutron and emitting an electron as the result of the change in charge. My questions are, 1. Why does the quark change? 2. How does it change and how does it change charge?

Hi, I heard before that wired keyboards emits radiation when a key is clicked. My goal is to build a keylogger based on this phenomenon (for fun, of course). I've already seen some variations of this idea, but they were all using wireless keyboard, where it is much more simple to detect and...

Hello! This is an old problem from the Estonian-Finnish open physics olympiad (2013) and I hope you will be able to lend me some help. 1. Homework Statement Sun-rays are focused with a lens of diameter d = 10 cm and focal length f = 7 cm to a black thin plate. Behind the plate is a mirror...

Hi This question may have already been answered elsewhere. If so please accept my apologies in advance. I am confused! The textbok(s) I am reading describe a whole bunch of different causes for there being temperature fluctuations in the CBM, so I am confused about which one(s) of these...

How are radiation sources like neutron or gamma/x-ray emitters used to detect materials? In particular illicit explosives and nuclear material and the such?

Homework Statement I could not fit the whole problem typed out but; Describe with a diagram, an absorption experiment to distingush between alpha, beta and gamma radiation. Homework Equations None required, written question. The Attempt at a Solution Source, absorbers placed in front of...

The question is to resolve a logical conflict. GR says as we fall into a black hole, an outside observer will see that event come to a stand still as if the falling object is hovering at the horizon. This stand still extends to infinite time. Unfortunately, I've read and hear the term...

Why is Planck radiation the greatest amount of radiation that anybody at thermal equilibrium can emit from its surface, whatever its chemical composition or surface structure?

Hello everyone, What is the average intensity of the background neutron radiation?

Hello everyone, Is it practically possible to detect a neutron source with an intensity of 0.1 Bq and each neutron having nearly 10MeV energies (and differentiate it from background neutron radiation)? If that's possible, what kind of equipment can be used? Do you need extremely sensitive and...