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.
In physics, velocity (speed) is the "change of position (spacial location) per change of time" and acceleration is the "change of velocity per change of time". Mathematically this is first and second derivative. Do further derivatives exist that correspont physical quantities like "change of...
Background: For electric dipole radiation, the energy and angular momentum lost by radiation from a system of charges by radiation is given by:
$$\dot{E}_{dip} = -\frac{2}{3c^3} \ddot{\textbf{d}}^2$$ $$\overline{ \dot{\textbf{M}}_{dip} } = -\frac{2}{3c^3}\overline{\dot{\textbf{d}} \times...
I derived the formula for the quadrupole radiation power emitted by a system of masses:
$$P=\frac{1}{45}\dddot{Q}_{kl}\dddot{Q}_{kl} .\quad\quad (*)$$ Note here that: (1) I am using geometrized units, so ##c=G=1##; (2) ##Q_{kl}## is the quadrupole tensor $$Q_{kl} = \int{(3x_k x_l - δ_{kl}\cdot...
In various books, blogs, etc., the Hertz dipole radiation is presented and visualized as field lines that lose their link to the pole charges due to the retarded value of the fields at distant points, lines that close on themselves and jump into space as waves. From this it can be deduced that...
How can an approaching observer receive the information from a source at a higher rate (as an accelerated recording), while the information-carrying radiation could not?
If I stand by a flying with constant speed charged particle, at my location the electric field will change as the particle get closer and further from me. So this change in electric field should create magnetic field and so on, producing an EM wave?
Hello, I want to ask about neutron contamination threshold. Is there a threshold for neutron contamination in tissue used LINAC that is safe and has been regulated by an international organization? thanks for your help.
I am interested to calculate dose rate (gy/h, rad/h) from a point source at a certain distance through MCNP. If I use F6 tally it will give answer in Mev/g which can be converted to Gray or rad by using FM card, but I don't know how can I find dose rate like rad/h or g/h.?
The figure is infinite out and in the page.
We need to find $$f_{ij}$$ means if $$I$$ is the total radiation plate i is emitting then $$f_{ij}$$ represent fraction of total radiation Falling on plate $$j$$ from plate $$i$$
$$So in general fab represent fraction of total radiation from a...
I've written it as :
The mentor indicated that this is incorrect. How can I write it correctly?
My try: $$ \sigma = 1.07 \times 10^{-8}W.m^{-2}.k^{-4} \pm 0.0243 \times 10^{-8} W.m^{-2}.k^{-4} $$
TL;DR Summary: Currently working on a project for lab where we're sending Geiger counters 100k feet into the air. Goal is to determine radiation as a function of altitude. Need some guidance.
Hi everyone,
I'm currently working on a project for lab where we're sending Geiger counters 100k feet...
Hello, I doing my thesis, I'm beginner in MCNPX. I want to ask about transformation in MCNPX, I want to transform this head phantom in inside and outside field ( radiation using LINAC from face to ear) in angle 90° and 270 °. Can anyone help me to solve this problem with transformation code?
In this video at 0:38 man say that unbalance current flow increase magnetic radiation far away, even few streets away from source..
1. Why radiation increase in these situation?
2. Is every system subject to that phenomenon and when unbalanced current happend?
3. Will emf meter show this...
Hi. No real physics background here so bare with me. Do magnets (ceramic ferrite and neodymium magnets) emit ionizing radiation? Many products use these types, including children’s magnet tiles and electronics. Can they pose a radiation and cancer risk as a result?
Does anyone have experience with radiation doses and measurement units in radiology?
I was looking at some DICOM metadata...
X-ray image of sinuses that include forehead sinus using Philips DigitalDiagnost C50
"Image And Fluoroscopy Area Dose Product" stood out to me since it is measured in...
I previously purchased a Geiger counter (GQ Electronics GMC-600+) for a university lab and have been confused about an elevated radiation reading from the envelope the Geiger counter came in. The envelope was a USPS Priority Mail bubble mailer envelope...
Hello,
I need to carry some simulations for my master's project and my tutor doesn't know much about simulations. I can't tell much since it is related with a private company but basically I'll have to simulate and measure the radiation emitted by some enriched uranium particles or uranium...
I managed to calculate the fluence of the scattered photons. However, not the transferred photons. In the solution sheet the fluence rate has an l22 in the numerator in the end of the solution sheet. Where does that come from?
Most general sources that describe the basics of ionizing radiation assert that the only type of radiation that can directly make other materials radioactive is neutron radiation (via "neutron activation").
Googling "does radiation make things radioactive?" produces a few examples, for...
Pocket dosimeter consists of a small ionization chamber, if a person having pocket dosimeter moving in a radiation environment, how the dose received by the man is equivalent to the dose showing on pocket dosimeter although the exposed area of a man is quite larger than the dosimeter ?
Is it possible to detect transuranic elements that may eventually occur during big astronomical events? I know that transuranic elements are radioactive, so we could maybe measure the radiation that is being emited, but how could we separate the radiation that comes from the transuranic elements...
We know that when a high energy gamma ray(E >= 1022 keV because the total energy of 1 electron at rest and 1 positron at rest is 511 keV) passes near a high Z(atomic weight) atomic nucleus interacts with the electrical field of the nucleus and there is a probability that this high energetic...
I ran a gel on electrophoresis that had proteins that were radio-labeled with 35s methionine, and in the process of imaging the gel (after 36 hr exposure on phosphor screen) I accidentally grabbed it with my bare hand. I'm getting very mixed messages regarding whether this is okay or not. Thoughts?
I'm slightly confused by what medical professionals/scientists say when they say to limit exposure to x-rays/CT/PET, etc. scans if possible, due to radiation. I'm also confused as to why we're often told to leave the room when a relative is getting such a scan, given that medical staff that...
I was trying to understand why some compounds appear colorless (transparent) and tried to give an explanation.
I take benzene as an example: it is a chromophore group in which there is π-conjugation, so a certain energy gap is generated between HOMO and LUMO. This energy gap is such that in...
Consider a source emitting a beam of photons. These photons pass through x thickness of material. The attenuation coefficient of the beam \mu is known.
We can write this formula
If I'm not wrong, this formula tells us the number of photons that passed through the material of thickness x...
The problem comes with solutions. However, I dont get the 3 steps in the solutions. Why do they calculate decay for 120min in step 3? And why is only the daughter nuclide relevant and no granddaughter? There might be something lacking in my knowledge about nuclear reactions.
Also, I don't know...
There is heating of the surface of the material using an electron beam. It is necessary to calculate how much heat will be released and build a graph of dependence. Please tell me how this can be done, which modules in COMSOL can be used?Thank you!
Hello. I have a quick question in regards to EMF radiation. In particular, I would like to know what quantity of microteslas a smart TV would emit. In particular, would it be unusual for a smart TV to emit in excess of 1000 microteslas even when turned off? Thanks.
There is a well-known Abraham-Lorentz equation describing radiative friction. Suppose a particle moves in an electromagnetic field.
ma(t)=q(E+vxB) + m(tau)a’(t)
By solving this equation numerically, I get non-physical solutions(runaway solutions) Although, it would seem that an electron in an...
I've been doing some research on the topic of radiation reaction force/self force in classical electrodynamics and although there are some discussions on the internet I would like direct answers to these following questions:
Is there a rigorous and universally accepted treatment of radiation...
The geometric configuration that I am adopting is the following, I hope you understand.
The optical fiber is positioned relative to the bottom surface at a height ##a## and an angle ##\alpha## with respect to the y-axis in the yz-plane with x = 0. ##b## is the distance between the origin and...
Hi,
I wanted some clarification on the mechanism for how EM radiation interacts with standard glass, namely IR, visible and high energy (UV and X-ray).
Looking online most sources seem to say the band gap is around 10eV. Since visible light is about 1-3eV visible light will be transmitted.
IR...
For this problem,
The solution is,
However, when they found the angle, they did not account for the uncertainty. I guess this is allowed still since the sine of the angle will still be greater than 1, correct?
Many thanks!
I got this question from my son last night.
If you Google "Why is Cherenkov radiation blue", you get this:
Somewhat more substantial is the Wiki article on the Frank-Tamm formula.
That formula ties the Cherenkov radiation wavelengths to the transmission characteristics at any specified...
In the solution below it says 22% goes to 0.0309keV. From the diagram above I interpret 22% goes to 0.1298keV with EC(L)/EC(K)=3.0 and not 4.4. Why is that wrong ?
Thanks alot!
Former USA President Jimmy Carter seems to be near the end of his 98 years, and was one of the original US Navy nuclear engineers. Over 70 years ago, he led a team that extracted out the world's first melted down core out of a Canadian reactor, himself going 90 seconds into the "dead zone" -...
I was looking at the gamma radiation data from IAEA's website:
(https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html)
and was confused by the absolute intensity listed in the page. I Googled it and it seems to be the probability of emission but why it doesn't add up to 100%?
For example...
Hi,
I want to try to solve this puzzle in my head.
They say that faster than c travel would break causality. And yet particles can travel through a medium faster than light can in that medium. But surely if that can happen then a particle can arrive at a place faster than information about the...
The commonly called value of the temperature at recombination is 3000 K.
According to this reference the process of recombination can be described by the Saha equation:
3.1. Recombination and the formation of the CMB
Recombination happens quickly (i.e., in much less than a Hubble time t ~...
First of all i tried to follow the textbook. Here they start of by modelling the atom as an harmonic oscilator:
Then they find the solution as:
They neglect the second term as omega_0 >> gamma which also makes good sense so they end up with:
So far so good. After this they state the...
I am not sure of the answer. But I am guessing that infra-red rays carry more heat radiation than ultra-violet rays, and the heat is instantly felt on our skin when exposed to both these rays. So what we feel is the heat sensation from infra-red rays and that sensation is missing when it's...
MCNP Output:
energy stopping power range radiation beta**2 density rad/col drange dyield
n collision radiation total yield corr
mev mev cm2/g mev cm2/g...
This is a topic that will be relevant for anyone who plans to use "realistic" artificial gravity (of the centrifugal kind, rather than the "acceleration-based" kind) in their stories - be it on spaceships or space stations:
How much of the ring walls has to be dedicated to radiation shielding...
Alright, since I’m still stuck on my sci-fi story because I can’t exactly outline the mid-point plot twist with a realistic catastrophe on board an interstellar spaceship, I thought I’d widen the scope a little — towards full-on open brainstorming:
What, if anything, can realistically go wrong...
The intense gravity near the event horizon causes complementary particles to pop into existence spontaneously. As local space-time is continuous through the EV, the same would be happening just inside the EV, only more so as the gravity field and gradient is greater. So near the singularity...
The Hawking radiation comes from a pair of complementary particles, an electron and a positron for example, coming into existence spontaneously near the event horizon as a result of the intense gravitational field. One particle gets captured by the Black Hole while the other escapes, taking a...
a. We know metals emit EM radiation upon heating or electric current. I'd like to understand more fundamentally how this phenomenon takes place, on the basis of the basis of band structure, and which electrons are involved ?
b. Classically, charges emit radiation when accelarating or...
I came across an academic article by Mary Olson entitled "Disproportionate Impact of Radiation and Radiation Regulation" (https://www.tandfonline.com/doi/abs/10.1080/03080188.2019.1603864). Based on data in BEIR VII, she illustrates that women are more sensitive to ionizing radiation than men...