What is Radiation: Definition and 1000 Discussions
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)
particle radiation, such as alpha radiation (α), beta radiation (β), proton radiation and neutron radiation (particles of non-zero rest energy)
acoustic radiation, such as ultrasound, sound, and seismic waves (dependent on a physical transmission medium)
gravitational radiation, radiation that takes the form of gravitational waves, or ripples in the curvature of spacetimeRadiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 eV, which is enough to ionize atoms and molecules and break chemical bonds. This is an important distinction due to the large difference in harmfulness to living organisms. A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively. Other sources include X-rays from medical radiography examinations and muons, mesons, positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic rays interact with Earth's atmosphere.
Gamma rays, X-rays and the higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum. The word "ionize" refers to the breaking of one or more electrons away from an atom, an action that requires the relatively high energies that these electromagnetic waves supply. Further down the spectrum, the non-ionizing lower energies of the lower ultraviolet spectrum cannot ionize atoms, but can disrupt the inter-atomic bonds which form molecules, thereby breaking down molecules rather than atoms; a good example of this is sunburn caused by long-wavelength solar ultraviolet. The waves of longer wavelength than UV in visible light, infrared and microwave frequencies cannot break bonds but can cause vibrations in the bonds which are sensed as heat. Radio wavelengths and below generally are not regarded as harmful to biological systems. These are not sharp delineations of the energies; there is some overlap in the effects of specific frequencies.The word radiation arises from the phenomenon of waves radiating (i.e., traveling outward in all directions) from a source. This aspect leads to a system of measurements and physical units that are applicable to all types of radiation. Because such radiation expands as it passes through space, and as its energy is conserved (in vacuum), the intensity of all types of radiation from a point source follows an inverse-square law in relation to the distance from its source. Like any ideal law, the inverse-square law approximates a measured radiation intensity to the extent that the source approximates a geometric point.
The way I understand Hawking radiation is that black holes decay by sucking in anti particles from the virtual particle pairs that are created right at its event horizon. I also understand that these anti particles reduce the mass of the black hole instantly when crossing the event horizon? And...
So I understand that a black body is a diffuse emitter, and that it radiates energy at a rate of σT^4.
I also understand the correspondence between a solid angle and the superficial area of a sphere.
dS=r^2sin(θ)dθd\phi=\frac{ds}{r^2}=d\omega=\frac{dAcos(\alpha)}{r^2}
What I don't...
So I understand that a black body is a diffuse emitter, and that it radiates energy at a rate of σT^4.
I also understand the correspondence between a solid angle and the superficial area of a sphere.
dS=r^2sin(θ)dθd\phi=\frac{ds}{r^2}=d\omega=\frac{dAcos(\alpha)}{r^2}
What I don't...
I was studying black body radiation and how quantization of energy solves the problem of ultraviolet catastrophe. But I have a very fundamental doubt. A black body can be assumed as a cavity with a small hole with radiation leaking out of it. As the temperature of the black body is increased we...
Dear all,
If I have the value of photosynthetic photon flux in unit [ micro mole per meter square per second] as an output for ultra violet sensor.
How can I know the corresponding wavelength of that radiation ? and can I know from that wavelength what is the type of the ultraviolet...
Alright if I have an object that's completely constituted of alpha radiation particles (emitting the +2 charge nucleus of a hydrogen atom), how would that be accurately detected taking into consideration that I don't have a Griegor Counter on hand?
Americium-241
To whom is able to answer this:
I think that when radiant energy get in contact with matter three basic phenomena take place:
1.- Transmission
2.- Reflection
3.-Absorption and emission
I think this three basic phenomena enclose all phenomena that can occur after the interaction
I wait for...
This is from Wikipedia:
1. What is really meant by "self-propagating", how it works?
2. How many electric and magnetic fields are in one wave?
3. What is the strength of those electric and magnetic fields?
4. What does -q and +q represent in the above diagram?
5. Why would...
I have a model set up, that is a cuboid, with a membrane half-way along - a bit like an impedance tube setup.
I've used Integration 1 & 2 with Explicit 1 & 2 to define an 'inlet' and 'outlet' at opposing faces of the tube. The Variables for the inlet and outlet are intop1(p0) and intop2(p)...
I have been struggling with the following; (apologies if this is a simple question)
After reading the Hershel experiment where with a prism light was used to split white light into a spectrum of colours and the red light was warmer than the violet light, then he placed a detector past the red...
Hello,
in Schwartz's QFT-book it says that:
"Classically, a box of size L supports standing electromagnetic waves with angular frequencies \omega_n = \frac{2\pi}{L}\left|\vec{n}\right|c (...)"
I wonder if the factor 2 is really correct, I only get this factor 2 if I suppose that eg. for...
I see this comet being chased by ESA, they said it is presently about 500 million km from the sun.
That puts the radiation received by that comet at about 10% (roughly) as what we receive on Earth, well at least on top of the atmosphere, at 1355 watts per meter ^2.
Looking at the size of...
Hi, As I understand it, the CMBR presents with a temperature equivalent to approx 2.5k. If a WMAP-type experiment was run to mapa radiation signature at a colder temperature, say 2, or 1.5, or 1 degree, would it find anything?
Thanks in advance,
Noel.
Would anyone have a different explanation and maybe an example of radiation flux? Here is the Wikipedia definition "Radiation flux is a measure of the amount of radiation received by an object from a given source", which is quite clearly explained.
I want to pump energy into a chemical species to increase its reaction cross section with another.
Typically these species react upon collision when their relative kinetic energy exceeds the activation energy. I want to find a way to increase the reaction rate for interactions at slower...
Suppose a point charge is accelerating uniformly. It emits EM radiation.
If an observer is co-moving with the point charge, the point charge remains at rest in his/her frame.
So I guess it does not radiate relative to the co-moving frame.
But someone told me that acceleration is absolute...
So everyone has made non-Newtonian fluid at some point in their lives (when you mix corn starch and water and get that awesome liquid/solid) well in one of my classes last semester we were asked to think of ways to aid in shielding from radiation and MMOD's (Micro Meteoroids and Orbital Debris)...
Definition/Summary
Hawking radiation is black body thermal radiation predicted to be emitted by black holes due to quantum effects-
'The vacuum in quantum field theory is not really empty; it's filled with "virtual pairs" of particles and antiparticles that pop in and out of existence...
So we are at a distance from the black hole R>2GM/c^2 where quantum fluctuations happen all the time.
How is it possible that every time the anti-particle ends up in the black hole(the one that will decrease her mass) and eaven if it's so,how can the other particle escape?if they are at a really...
Any object can emit and absorb radiation and the power of emission can be represented by the Stefan-Boltzmann law: P=AεσT4
In many texts the net power radiated is the difference between the power emitted and the power absorbed:
Pnet=Aεσ(T4-Ts4) where Ts is the temperature of surrounding...
I understand that, for example, a thick enough sheet of lead can absorb gamma radiation, but I want to understand what actually happens at the molecular/atomic/subatomic level. Also, can the same logic be applied to cosmic particles? I have tried Googling for an answer, but to no avail. Can...
Can you classify ordinary light as ionizing radiation?
Okay. So, I'm thinking that ordinary light has about 2 eV of energy per photon.
But, alpha, beta and gamma ray have huge eV from 0.1 to 10 MeV.
However, could there be a case where the 2 eV could knock out an electron and cause...
Hello guys.
From my understanding of the Hawking radiation, it is a consequence of QFT in curved space time. The fact that a uniformly accelerated observer sees the Unruh radiation means that by the equivalence principle, a stationary observer at a distance from a black hole will see Hawking...
If a blackbody is in equilibrium with the surrounding electromagnetic field, the power emitted by the surface of the blackbody will be related to the energy density of the electromagnetic field by P=\frac{cu}{4}. Try as I might, I haven't found a good derivation for this equation (the...
So as I understand it, Hawking theorized that due to the behaviour of virtual particles on the event horizon of a black hole, eventually the black hole would "evaporate" through what was coined the Hawking Radiation. But what I'm curious about is Hawking's interpretation of the event in that...
How does the blackbody radiation prove the existence of photons or quanta as Planck described it, I've understood how the photoelectric effect proves the existence of photons, but the blackbody radiation seems quite vague to me. I would like a basic explanation for this, thanks in advance.
It is given in my book that the phenomenon of black body radiation can be used to prove the particle nature of light. They have also mentioned that the wavelength-intensity relationship "cannot be explained satisfactorily on the basis of wave theory of light." But why?
Thanx in advance...
I have a quick question about blackbody radiation.
Planck modeled a blackbody as a collection of harmonic oscillators. Then he assumed that each oscillator could only have a energy E equal to nh\nu, where \nu is the frequency of the oscillator.
My question is, how can a collection of...
Hey, I'm new here but I was hoping you guys could help me out. I am currently studying Waves mainly using MIT's course 8.03 - Vibrations & Waves.
I am now at a point where I have almost finished reading AP French and entering EM Waves. Unfortunately French decided (for whatever reason) to not...
I've heard that the Earth's magnetic field protects us from radiation but am curious as to how this works.
I assume it would have something to do with charged particle motion in a mag field because radiation is ionizing but I can't seem to nut out the mechanics behind it.
Thanks in advance.
Does anyone know of any papers describing the interaction between radiation and gas. Specifically I am trying to find out is the relationship between PPM and the flux of the radiation. At what point do the two intersect to give a measurable response and does the interaction increase linearly...
$$\begin{equation}
0 = ({\rho}_m + P_m)u^{m}_iu^{m}_j + \frac{4}{3}{\rho}_ru^{r}_iu^{r}_j
\end{equation}$$
where i,j = 1,2,3 and different. That is the off-diagonal elements of the tresstensor for matter fluid and radiation fluid.
The energy conditions imply that
##\rho_m + p_m > 0## and...
Hi
I need some helps to find a proper portable instrument/equipment to measurement radiation leakage in a radiological diagnostic facilities of hospitals.
Thanks in advance
Basically need more help checking my answers, I think it's better if I provide the full context:
A radioactive substance with an initial mass of 300mg has a half-life of 2 years.
a) Write an equation to model the mass of the material over time.
Let A = mass of the material
Let t = time
A =...
Hi as far as I have understood: Blackbodies are physicsl objects which absorb electromagnetic waves at ALL frequencies. And the only light they radiate is determined by their temperature which means They don't reflect any light shined on them, they only emit Energy from their temperature...
Here is my understanding, please correct me if I made any mistake
Quantum physics theory suggests that information (the wave function, state, etc.) cannot be destroyed. All matters fall into a black hole will not be able to escape, which means all information of these particles stay inside...
I've had to work with p33 and cesium-137 for a few of my labs for classes and for the past few weeks I can't seem to get myself to stop worrying about contamination.
It seems irrational but I'm wondering exactly how dangerous both types are?
Thanks for your time
Why is it that we observe a continuous spectrum in black-body radiation not discrete spectral lines dependent on the composition of the black-body?
A niave understanding is that it relates to the complexity of the atomic structure of the black-body as well as thermal motion of its constiuent...
Hawking Radiation and the "Decay" of Black Holes
I have been doing a lot of reading and thinking about certain quantum mechanics so that I can try and wrap my head around how it all works. However I have come upon something that I cannot find a good explanation for.
I was reading about...
Homework Statement
A light bulb has an internal filament with a total surface area of 2.5 X 10-3 ft2 that operates at a temperature of 2240 F. The filament has an emissivity of 1.0 and radiates through a vacuum to the glass wall of the bulb. Only 10 percent of the total energy emitted as...
Homework Statement
Cheese Board Pizza just hired me to design a radiant pizza warming system. The pizza must be maintained at 250 F until the order is picked up by the delivery driver. The one square foot pizza sits on a ½ inch thick ceramic pan (k = 0.50 BTU /hr ft F) on a counter that is at...
Homework Statement
Part (a): Show the Commutation relation [x, [H,x] ]
Part (b): Show the expression by taking expectation value in kth state.
Part (c): Show sum of oscillator strength is 1. What's the significance of radiative transition rates?Homework Equations
The Attempt at a Solution...
Homework Statement
The temperature of a blackbody is 500 C. If the intensity of the emitted radiation, 2.0 W/m^2, were due entirely to the most intense frequency component, how many quanta of radiation would be emiteed per second per square meter?
Homework Equations
λmaxT = 2.90 x...
Hello All,
Apart from using undulator or wiggler are there any big difference between synchrotron radiation and FEL? Because I notice it looks similar. In both case electron is forced to travel like a sine wave...and synchrotron radiation is produced..
Also what is the difference between...
Someone on another forum shared with me that a 6L6 vacuum tube exhibits a blue dot when in operation that is supposed to be Cherenkov radiation. I say nay, as I have worked out the relativistic velocity using $$KE={ m }_{ 0 }{ c }^{ 2 }\left[ \frac { 1 }{ \sqrt { 1-\frac { { v }^{ 2 } }{ { c...
Hi all,
I have a couple questions about radiation from radioactive elements. I've read a lot of articles on the different types of radiation given off by elements undergoing nuclear decay (alpha, beta, and gamma)
but I haven't been able to answer the following question:
What is the...
Some article made mention of intense radiation on Mars. Does that mean Mars lacks a magnetosphere? I figured it would be about like earth, with a molten iron core.