Radiation Definition and 1000 Threads

when I read about the ultraviolet catastrophe on the internet I get a severe headache, and what I read in it doesn't stick in my mind, and my textbook says: "The classic physics failed in explaining the black body radiation because as a classical point of view the radiation is electromagnetic...

Some days ago, i read, that there is a plastic, that should be capable of protecting from interstellar radiation. I would be interested in further information about this plastic. Someone here who has some material, i could take a look at?

can string theory reproduce hawking radiation in non-extremel black holes in 4D? i.e physically realistic black holes. do they exactly match hawking's calculations? what is the interpretation of hawking radiation in string theory?

Homework Statement Calculate the number of modes in a cubic cavity of length a=2.5 cm in the wavelength interval (λ1,λ2) where λ1=500 nm and λ2=501 nm. What's the total energy which radiates from the cavity if it's kept at a constant temperature of T=1500 K. Homework Equations I imagine these...

Hello all, this is related to a project that I am working on. It is not directly related to the project but as part of it, I thought it would be a good idea to check the temperature difference that I need to maintain in order to effectively transfer a certain amount of heat between the TH in a...

It has been demonstrated that it is possible to make humans hear sounds using waves. Abstract From Journal of Applied Physiology Is there a practical method for shielding? I mean using materials for simple attenuation, and/or altering characteristics of waves (frequency, phase and/or amplitude).

Is there a meaningful way to convert the energy of an electromagnetic wave to a temperature? I mean this more along the lines of how the universe has a temperature of 2.7 kelvin due to electromagnetic radiation. I'm honestly just curious to determine the temperature of the universe after nearly...

Homework Statement When a particle is accelerated toward another particle it is giving off electromagnetic radiation in the form of gamma waves. After a particle is annihilated, pions are transferred between the particles which turn into gamma waves which decay into (for example) an electron...

Homework Statement a) Estimate the radiation pressure due to a 100 W bulb at a distance of .08 m from the center of the bulb. b) Estimate the force exerted on your fingertip if you place it at this point. (Assume an area of .0001 m2 for the fingertip.) Homework Equations F=PradA The Attempt...

When antenna receive the radio signal does it reduce the actual radio signal strength or strength indeed depends on the dispersion loss and other dielectric absorption? If antenna doesn’t reduce the radio signal strength(power), how it generates the current in the receiving antenna circuit? How...

In a discussion with a friend I am unable to explain to him why at this moment we still can detect cosmic background radiation. According to his reasoning the radiation that originated from the big bang should have passed us long ago. Where in fact does this radiation that we now detect come...

The mass of a neutron is approximately 1.674927471×10−27 kg, but is this always the case? For example if a neutron undergoes negative beta decay (i.e. an electron and an electron anti-neutrino is emitted) and then positive beta decay, will this not mean that the final mass of the neutron is now...

So we are doing Radioactivity lab at second year undergraduate. I am confused about the workings of the silicon radiation detects we are using even though the demonstrators tried to explain. We are detecting beta and gamma radiations by placing sources above a silicon detector that have a small...

Could this possibly be what the inside of a black hole looks like? aka our Universe resides in a black hole and this area is the event horizon slowly becoming more desolate as Hawking radiation occurs on the opposite side.

http://lookpic.com/O/i2/73/DYktKEGg.jpeg Hello Dear Friends We produce Lifting Electromagnet for Steel Scrap charging of Induction furnace, bottom plate of electromagnet is made of Stainless steel . my question : Can We use AL OR SILVER Spray for Spraying bottom plate that Radiation heat...

Are Unruh radiation and Hawkins radiation manifestations of the same basic phenomenon?

Homework Statement Currently, the density of matter ##\rho_0^M## and of radiation ##\rho_0^R## have values of approximately ##10^{-29}## g/cm^3 and ##10^{-33}## g/cm^3 respectively. Estimate the ratio of the cosmic scale factors ##a_{eq}## (scale factor at equality) and ##a_0## (scale factor...

EXPERIMENT ABSORPTION OF γ - RADIATION IN LEAD AND CALCULATION OF ABSORPTION COEFFICIENT µ Using equation (3) / slope of graph lnC vs d - estimate µ. This should be in units of per meter (m-1 ). The formula in the analysis are as follows : 1. I = I0 e-μd 2. C(d) = C0 e-μd 3. lnC = lnC0...

I thought Hawking radiation was a virtual particle pair emerging from nothing, one particle falling into the event horizon and the other particle tunneling out of the event horizon. Then I read this - https://www.physicsforums.com/insights/vacuum-fluctuation-myth/ and now I think a virtual...

I plan to publish submit a piece of publication about research on tritium produciton and discharge in PWR. It should be classified into nuclear engineering or radiation protection? Could you help to recommend some magzines of SCI or EI? It's better if the magzine has a fast period of reviewing...

I was reading this article which talks about the theoretical model behind blackbody spectra: http://www.cv.nrao.edu/course/astr534/BlackBodyRad.html At the start, it mentions standing waves in a cavity. Standing waves in this model consist of an integer number of wavelengths. The standing waves...

The formula for the radiation pressure P in n-dimensional space for a given internal energy density u is ##\frac{u}{n}##. I would really appreciate it if someone could provide a link that gives a simple derivation of this formula for dummies like me.

http://imgur.com/a/8B1EV http://imgur.com/a/8B1EV http://imgur.com/a/8B1EV As shown, an X-ray tube (source) is striking a fluorescent plate. The source has a large angle (100+) that the rays are emitted. How is radiation distributed (spatially and energetically) in this set up? Does this...

Do falling charged particles radiate? Also, if I hold a charge still and bring a large mass close to it first on one side then another so that the particle sees a sinosoidally oscilating gravitational field will it radiate?

This might be a very stupid question :(, but I am confused. So I did an experiment. we had radioactive material which was emitting beta particles, and we were using geiger counter to measure pulses (ionized beta particles). We were supposed to measure the time it takes for the geiger counter to...

In the 1953 science fiction novel Childhood’s End by Arthur C. Clarke, characters use two crossed fields in outer space to block some of the solar radiation traveling towards earth: “Somehow, out in space, the light of the Sun had been polarized by two crossed fields so that no radiation could...

Hi, just trying to better understand this concept of electromagnetic radiation. My understanding thus far is that it is a traveling disturbance in the electric field. This picture here seems to help me see what is happening...

Homework Statement A patient is treated for cancer using radiation from a cobalt-60 unit. Exactly 1.5 years later another patient is treated for the same cancer using the same co-60unit previously used. How much longer would treatment be for the second patient? Homework Equations Decay...

Air stops most cosmic radiation. Yet some particles do reach sea level. The cosmic radiation at sea level is estimated at around 300 microsieverts per year. Cosmic radiation also causes nuclear reactions in air that stops it. Many isotopes created by cosmic radiation are stable, or short lived...

Is it possible for enough energy to be dissipated in the form of gravitational radiation in a two-body system to allow for capture? From what I remember, you would need extremely massive bodies passing extremely close to each other: I'd like to know how massive and how close. It has been a few...

Hello.Looking at Jackson's ch 9 on radiation, I am trying to calculate the fields E and B from the potentials in the far field but it is very confusing. Given now the approximation for he vector potential \textbf{A}_{\omega}(x) = -ik \frac{e^{ikr}}{r} \textbf{P}_{\omega} with...

Homework Statement *Main ideas in bold[/B] Investigation of the inverse square law of light radiated from a light bulb. (done method, diagram, results and graph) Independent variable = the distance from the LDR (cm) Dependent Variable = resistance (k/ohms) Brief method: using an LDR, bulb...

Do atoms give off radiation that determines the colour? I want to understand this, please give me explanation.

This question is regarding the dependence of Planck's law for black-body (BB) radiation intensity (or integrating over a hemisphere, the emissive power, E = pi * I). Physically speaking, why is it that a BB emitting in a medium with n>1 (n being index of refraction) emits a higher power/area...

In Kraus book on antenna (3ed page 203) example 7-4.1 the difference between those antenna is (to my understanding) only the wave length. How could they have different radiation pattern?

Hi, I'm a high school science teacher. Most textbooks classify EM radiation as kinetic energy. But this doesn't seem right to me. As a photon is massless it's hard to see how it can have kinetic energy which is 1/2 mv^2. It could be said that it has energy hf and therefore mass hf/c^2. Then its...

The wavelength is inversely proportional to the foton energy. So, the limit can be stated by the mass of the full universe. But how much near that limit can the light be?

IIRC , a perfect sphere will not be detectable with a gravitational detector, but an ovoid shaped body will, why is this so? or am i wrong.

I am curious as to the formula for radiative power due to a single object in forced circular motion. In particular, I am interested in the power of gravitational radiation for volumetric invariant mass densities for both the low density Newtonian limit and the high density general relativistic...

I need clarification on the difference between a “force carrier” and “radiation.” Imagine two electric charges separated by a distance “d” but not moving. They exchange “force carrier” photons which tell the electric charges to attract/repel. But you can’t see these “force carrier” photons...

Hi Guys Studying thermal radiation here and I am kinda stuck at one point Kirchhoff law states that at thermodynamical equilibrium, the amount of energy absorbed must be reemited. But before the system reaches equilibrium, is there a model to predict how much energy of these photons absorbed...

I come to this conclusion because a mazer amplifies radiation; a transistor amplifies electricity.

Back in 2005 Shahar Hod submitted a paper (http://arxiv.org/abs/hep-th/0510089) proposing that Unruh radiation from quarks inside nucleons is of a magnitude comparable to the mass of a quark. This concept has been discussed in previous threads...

Homework Statement Homework Equations Between Radio Waves and Protons is where my confusion lies; Online I read that Radio waves are non ionizing but if that's the answer then how are protons ionizing? I mean it's no even included in the types of ionizing radiation here...

Can high energy incoming protons and electrons be absorbed and their energies remitted by photons? If so what are the typical ranges of energies emitted and are they heading in the same direction as the original emission if we had a sheet of metal being bombarded by those protons and electrons?

I'm reading this article... "Hawking proposed that the Universe is filled with 'virtual particles' that, according to what we know about how quantum mechanics works, blink in and out of existence and annihilate each other as soon as they come in contact - except if they happen to appear on...

First, what are these 'particles' that appear with their negative mass counterpart and suddenly disappear very quickly and why do they do that? Now, I know the positive mass ones are allowed to escape the event horizon while the negative mass doesn't, thus fall into the black hole, but how does...

If an observer accelerates through a simple vacuum, it is often said that they see Unruh radiation with acceleration of ##2.5*10^{20} m/s^2## equivalent to a temperature of 1K, but I haven't seen the polar distribution described, one might assume it was from 'ahead' of the direction of...

Yesterday I decided to carry out a cloud chamber experiment for a school assessment. I used "100%" isopropanol and around 2.5 kg of dry ice. After a wait of approximately 30 minutes, the particle tracks began to appear. I placed a weak source of Americium-241 sourced from a smoke detector (1...

So hawking radiation is a phenomenon thwt happens when a pair of particle-anti particle are generated from vacuum according to Heisenberg uncertainty principle at the horizon of e event is that right? And the negative particle "falls" into the black hole while the positive one escapes as hawking...