Radiation Definition and 1000 Threads

This isn't really a homework question, but I felt it was better suited here than in General Physics. I'm looking for more of a general explanation than anything. I was able to do my homework for this section on my own (mostly), but I feel like I still really have no idea what is actually going...

Hello, When did the really first radiation occur in the universe? I'm very confused from different sources: 1." The oldest radiation in space comes from 380 000 years after the big bang. 2. In the photon epoch three minutes after the bigbang was almost only gamma radiation. 3...

Where would you use our new radiation detector? We are a student team from the Vienna University of Economics and Business. Currently we are working on project with the research center CERN and try to find different application possibilities for an innovative technology by interviewing...

Hello All, I have been trying to understand the exact contribution of our legendary physicist, Dr.Hawking and found that Hawking radiation is amongst one. Is it that Hawking radiation is the first attempt to unify, general relativity, quantum mechanics and thermodynamics which led to the...

Here we have question with answer Could please explain to me the answer of this question ? and can explain to me why we don't use area 2pi . r^2 because we have pipe ? and how we can know this combined modes ? I mean conduction and radiation ? In addtion , As I know s = the...

Looking for a quantum-based explanation as to why solids, when heated, emit radiation as a continuum, rather than discretely. Gas will emit discrete spectral lines when heated. Somone already suggested to me that there may be many random purtubations to the discrete energy levels in a heated...

Wikki says the following with respect to Unruh effect: http://en.wikipedia.org/w/index.php?title=Unruh_effect&oldid=563459371 I'm not at all sure it's accurate though. I seem to be getting myself more confused as I try to think about this, starting with the issue of whether the temperature...

Hi, I need help in calculating the view factor F2-2 in the geometry that attached below. I tried to use the crossed string method for calculating the view factors but I'm not sure if its right. can anybody give a hint how do I find the view factor F2-2? Thanks, Pranav

If the radiation flux is calculated as: F = \frac{L}{2*pi*r^{2}} where L is the luminosity of the source and r is the distance from the source and the count rate of a scintillator \frac{number-of-scintillations}{time} What is the relationship between them? There obviously should be one, as...

I am having a lot of trouble understanding this concept. It seems to be the intersection of many theories: electrodynamics, special relativity, and quantum theory. Classical electrodynamics and quantum theory apparently have two different conceptions of what an EM wave is; in classical...

consider energy for a damped electric oscillator . ("f" indicates the dipole moment of the oscillator) in the absence of the damping force U= \frac{1}{2}kx^2 +1/2 (\frac{d^2x}{dt^2}) ^2 and the energy conservation tells us dU=0. but if there is damping force we get the following...

Homework Statement Venus and Earth may be regarded as behaving as black bodies. The mean temperature at the surface of Venus is about 600K and at the surface of Earth is about 300K. Which of the following is the best estimate for the ratio...

Hello, I am having a lot of trouble in determining the difference between an electromagnetic field and electromagnetic radiation. Is an electromagnetic field caused by electromagnetic radiation within the space of which the field acts over? However if I am right a point charge that is not...

1) Why can hitting a heavy metal target with high-speed electrons produce X-rays? 2) Alpha particles have a larger mass and lower speed. Thus, they are more likely to knock electrons out of air molecules. Why? Is it about momentum? I thought particles with high speed can knock electrons out of...

Hello, I am at present reading about black-body radiation and the derivation of the Rayleigh-Jeans law. I have a few queries, and am hoping they can be answered somewhat simply. What exactly is the mode of an oscillation? Why do the waves in the box have to be standing, and what exactly...

Bear with me, I am a chemist :shy: As far as I understand, every accelerating charge emits electromagnetic radiation. In mass spectroscopy charged molecules/parts of molecules move in the magnetic field which bends their trajectories using Lorentz force. That means they are accelerated...

Hi all, to begin this is my understanding of hawking radiation. A particle/anti-particle pair is generated. one particle outside the event horizon of a black hole, the other inside. The gravitational force "boosts" the one particle into being real. this energy is compensated for by endowing...

Hi all, I was wondering if, when a beam of light is pulled towards a black hole , because it can't accelerate, it is blueshifted? Thanks in advance.

U = Th + alpha rays 92p 90p 146n 144n I have heard that if n/p ratio exceeds 1.56, the substance becomes radioactive. Now, for Uranium, n/p ratio is 1.59. It gives out alpha rays in order to gain stability and in turn forms Thorium. n/p...

Homework Statement A laser beam of intensity I reflects from a flat, totally reflecting surface of area A whose normal makes an angle θ with the direction of the beam. Write an expression for the radiation pressure Pr[θ] exerted on the surface, in terms of the pressure Pr[p] that would be...

Homework Statement Radiation of intensity I is normally incident on an object that absorbs a fraction frac of it and reflects the rest back along the original path. What is the radiation pressure on the object? Homework Equations Radiation pressure Pr (force/unit area) Pra = I/c...

Homework Statement At what wavelength does a cavity at 6000 degrees Kelvin radiate most per unit wavelength? Homework Equations $$\rho_T(\lambda)d\lambda=\frac{8\pi{hc}}{\lambda^5}\frac{d\lambda}{e^{{hc}/{\lambda{kT}}}-1}$$ The Attempt at a Solution I'm pretty new to this whole...

1. Problem statement i am trying to calculate the momentum and energy of the products in the reaction 7Be4 + e -----> 7Li3 + neutrino 2. Relavant equations p = mv mass of 7Be = 7.016929 u mass of 7Li = 7.016004 u 3. The attempt at a solution i know that after the electron capture, the...

Hi, What is the difference between Matter and Radiation?

Are gravitons and gravitational waves analogous to photons and EM radiation?

The hypothetical Hawking radiation means that a set of baryons can be finally transformed, "evaporate" into a massless radiation - that baryons can be destroyed. It requires that this matter was initially compressed into a black hole. If baryons can be destroyed in such extreme conditions, the...

"The cosmic microwave background radiation" is an electromagnetic radiation observed in all directions of the sky and presents a profile type black body with about 3 K temperature. The fact that this allows us to infer the conditions of evolution of matter with radiation of the universe?

I've heard tell that a mission to the Galilean satellites is difficult for many reasons, but radiation is one of them. Is it safe to say that above all, the worst radiation is when you are landing and have landed on the surface of the Galilean satellites, because you are in Jupiter's Van Allen...

Hello! I am hoping someone could help. I have no idea where to start on this, and have been flipping pages for an hour or so trying to figure it out. Find the spectral range Δλ over which a blackbody's intensity B(1/2) is brighter than half of its peak value B(peak). (In other words, find the...

I was playing with an old crt TV and a small loop antenna earlier and noticed that when I hold the antenna vertically in front of the TV I get one solid spike at around 15 kHz. When I hold the antenna horizontally I get a multitude of spikes that are not there when I turn off the TV. This...

Hi there, I've been studying mechanisms by which high-energy radioactive decay products (beta particles, x-rays, gamma rays) are attenuated as they pass through matter. From my readings in introductory and intermediate level textbooks, the general mechanisms by which these particles and rays...

And if so, at a rate faster or slower or the same compared to at earlier times of the universe?

Hi, I've got a simple question regarding the maximum of the spectral energy density in Planck's black body radiation. It turns out that if you calculate which frequency has the most power associated with it (i.e. maximize R(\nu)), then you do it with wavelength as well, and compare, they're not...

Hi, I recently did a homework problem for my introductory Quantum Mechanics course and in the problem we were given the sun's temperature in Kelvin as well as the diameter of the sun and instructed to calculate the rest mass lost per second to radiation by the sun. I was able to solve the...

Hi, When a photon is emitted by an atom that has had an electron move energy levels, does the resultant wave dissipate 360 degrees in 3d or have a direction based on the movement of the electron. I'm thinking that my question reflects a lack of understanding of waves and forces.

By De-Broglie,light also exibits matter property. According to him, wavelength=planck's constant/ momentum. And again momentum is the product of mass and velocity. We again know that, mass of light i.e. photon is zero. Then from De-Broglie's equation, is the wavelength of light infinity? If...

Energy Of A "Single" Photon In Em Radiation? Is the energy of all photons in em radiation same? That is, say light differs from radio waves only in the number of photons per second

Does anyone have access to the current data about solar radiation reaching Earth's surface ? The most importaint is the UV range divided into UV-A, UV-B and UV-C. If not, then data from the past few years would also be fine. I need it for research but I cannot find anywhere such information.

If I have a charged particle traveling into a constant B field it will bend its path and emit cyclotron radiation. If a magnetic field can't do work then what caused the charged particle to change its kinetic energy. I guess if I was in the electrons rest frame their would be an E field in...

if you cool a radioactive material until it started to exhibit macroscopic quantum effects would it still radiate randomly or would it emit radiation in some coherent way?

Hi, I am just trying to understand the basis of radiation pressure. I understand radiation pressure due to absorption, but I am having a hard time understanding the radiation pressure due to reflection. From what I understand there will be an incoming photon with momentum p = E/c. The normal...

Relict radiation has spatial fluctuations: hot and cool spots. Of rather modest amplitude, but yet detectable. Have these patterns undergone any change? Galaxies are supposed to form a few hundred million years after big bang. If you watched a given hot spot of relict radiation, would...

This is GR9277, Problem 69. I know nothing about this thing. At 'http://grephysics.net/ans/9277/69' someone said it's about Cherenkov radiation. I think this is about interaction of charged particles with matter. In what course is this covered? What book do you recommend for studying this?

Just a thought because of the anomalous Planck satellite cmb data, and the second largest continuous structure in our solar system that almost fried the pioneer probe... Jupiter's magnetosphere which is known emitting radiowaves.

All bodies with a temperature emit electromagnetic radiation also known as thermal radiation or blackbody radiation. If I understand it correctly, the origin of this is the thermal motion (acceleration) of the atoms and their included positive and negative charges leads to EM radiation...

Homework Statement Hi everyone, I'm working on an assignment and am totally stumped by this question: A horizontal cylinder is heated electrically. The cylinder is supplied with a current at a DC Voltage. Using the data supplied and allowing for both natural convection and radiation...

both involve a charge carrier undergoing centripetal acceleration thereby producing radiation from the acceleration; so what's the difference?

basically any time i have an arc, i have electrons flowing in the opposite direction to the field gradient. so when the electrons reach the other side, they will be stopped, which will then produce an EM wave. In, class, my professor drew the direction of radiation in a particular direction, but...

It is known that a charged particle moving with some acceleration emits electromagnetic waves. For example, this may be a particle moving at a constant speed on the circle. In this case the radiation of a particle is called the braking radiation, the cyclotron radiation, or the synchrotron...

My problem is how to calculate the radiation measured from a moving star. I figure there's two ways to do it, both of which I go through below, but they do not produce the same answer! For the first part everything is in the rest frame, \mathcal{O} , of the star. The star emits N...