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.
a) For a flat universe ##(k=0)##, so ##(1)## simplifies to ##\dot a^2 = \frac{C_r}{a^2}##. The solution to this first order, separable ODE (given the I.C. ##a(0) = 0##) is
\begin{equation*}
a(t) = \left( 4 C_r\right)^{1/4} t^{1/2} \tag{2}
\end{equation*}
We switch to conformal time by...
Hello everyone!
I hope you all doing well :) I am having a trouble with detection the radiation in lattices. i am adding the input and the result file here for makes everything clear,
If someone can help me i would really be appreciate!
thank you!
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<mentor: moved to Biology>
How did you find PF?: While searching to find the amount of radiation in plants.
I am searching to find research on the amount of inherent radiation in plants.
If plants have inherent radiation, obviously digesting plants with radiation is not a prudent thing to do...
While watching the MIT online opencourse videos about ionizing radiation physics some questions came to mind.
Let me first clarify and reinforce some basics by asking them to you. I understand this might be long, please forgive me. I will appreciate your time.
1) A GM tube consists of a chamber...
Black body radiation formula contains power and exponential terms. Electric discharge in a gas results in the ion acceleration; the ion distribution comprises power and exponential terms too.
Any connection between these two phenomena (i.e. black body and potential) could be established?
Hello All:
i saw some youtube videos on testing IR controllers on normal with no add ons Cell phone camera and the cell phone screen is showing signal emitted by the IR LED of the remote controller , how the cell phone camera sensor are able to register a signal from an IR LED , the pixle in...
For a planet to be able to support life, it needs to have a source of energy. In our case this energy comes from the sun.
But in this paper, the author argues that a rogue planet (a planet that has been ejected from its stellar system and no longer orbits any star and is wandering in...
I was reading an old thread - Radiation Damage In metals from Gamma rays - https://www.physicsforums.com/threads/radiation-damage-in-metals-from-gamma-rays.826449/ The thread is long dormant and wasn't productive, but based on what I've learned over the last 5 years, I would change my response...
In this video How we know that Einstein's General Relativity can't be quite right - YouTube , Hossenfelder says: "The [Hawking] radiation is entirely random and does not carry any information..."
I have heard and read this from a number of other sources, and never understood. Completly random...
Hi! I’m really struggling to solve the last part of this problem, from where it says “Idem for an infinite plane with the same brightness B. And the same for a square surface with side L.”.
Could anyone please help or point me in the right direction? Thank you so much in advance!
I took Inorganic Chemistry I and Physics in high school. I took Inorganic Chemistry I and about half of Inorganic Chemistry II (dropped out mid-semster of Inorganic Chemistry II) in college. My Physics class in high school was just regular physics, not AP Physics, so I have never taken a...
I am computing the radiation pattern for that I have to calculate the power per solid angle I found $$m( magnetic moment)=I(t)A$$ where then i took the cross product with $n=sin(\theta)cos(\phi)i+sin(\theta)sin(\phi)j+cos(\theta)k$ After that I moved towards computing the E and B which I know...
Suppose there are two free electrons. Their mutual repulsion causes each to accelerate. Is there EM radiation?
Suppose those electrons are loosely bound to a nucleus, as in a metal. Is there EM radiation?
I am really stuck at this question, i would appreciate any tips you have. I already try to goes with series but the calculation is getting harder and tiring, so probably this is not the right way.
According to this link https://www.sciencemag.org/news/2020/07/how-atomic-bomb-survivors-have-transformed-our-understanding-radiation-s-impacts even at radiation doses as low as 0.005 gray, there is still a risk of cancer over long term. I have read some Radiation Effects Research Foundation...
Summary:: I teach high school (grade 12) and have always struggled with teaching about electromagnetic radiation. I'm looking for resources aimed at laypeople about EMR that may give me some ideas on how to teach it more clearly.
I teach high school (grade 12). We have just finished a unit...
Well, the title pretty much sums up my question. I want to know about electromagnetic radiation and the effects on human health in your opinions and knowledge!
I have done research into the topic and also gone down the road of things like wifi(modern technology) effects on health and most...
Both alpha and beta radiations can only travel short distances through air as they're not as penetrating as gamma radiations. How long gamma radiations with 22 MeV energy can travel in air? Is it meters, kilometers, miles, etc.
Is there a difference between a lower energy gamma ray and a higher...
Hello everyone, I'm looking to estimate the variation of degassing on a horizontal tank of VC (vinyl chloride) due to solar radiation.
The feed flow is continuous but the outlet is batch flow. So there is a lot of variation of liquid level in the tank (constant pressure).
To avoid a lot of...
Hi everyone, sorry we are talking about pulsed power accelerators again. In this context, it is about the HERMES III again.
According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf HERMES III, a 16 terawatt pulsed power accelerator at Sandia National Labs, which fired electron beams...
In addition to the usual alpha and beta particles visible in my condensation cloud chamber, I see occasional tracks that seem highly energetic -they easily penetrate the entire width of the cloud chamber (10-12 inches) going in one side and out the other. More mysteriously, their orientation is...
According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf the big pulsed power accelerator, HERMES III, generate electron beam with peak energy at 22 MeV and average electron energy at 16 MeV and the resulting photon energy which is bremsstrahlung radiation is approximately 2 MeV...
Some people said if it is originated from electrons then it is X-ray but if it is originated from the nucleus it is Gamma ray. But people can produced X-rays and Gamma rays by Bremsstrahlung process and in Bremsstrahlung process it is resulted from decelerating or braking electrons. So, Gamma...
According to this link https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf, HERMES III at Sandia National Labs can generate very large area gamma rays by converting the electron beam into bremsstrahlung radiations after hitting the tantalum target. As we can see in the isodose contours in the...
These pictures below show four isodose contours of HERMES III with different anode-cathode gaps. The radiation produced are gamma rays. More informations can be seen here in the article https://www.osti.gov/biblio/6233581-hermes-iii-gamma-ray-facility-simulation-technology-laboratory-guide-users...
I just realized I'm having a problem in understanding this.
So let's take an example the CMB is around 160 Ghz and the blackbody temperature within this frequency range is 2.7K which is rather cold as it is close to absolute zero.
Then let's take another example, Iter plasma will achieve about...
Can you compare the energy loss of electrons and protons due to the radiation they emit? In fact, I want to know which of the two loses more energy when it emits radiation.
According to https://www.osti.gov/servlets/purl/7234564, the HERMES III which stand for High Energy Radiation Megavolt Electron Source accelerator is "capable of delivering a peak dose of ~100 krad (CaF2) over a useful area of ~1000cm2 (area where dose is greater than 50% of the peak dose) in a...
t is Torque
I is the inertia moment
P is the power
c is the constant light speed
r is the spot distance to the fiber
p is the torsional constant
theta is what we want
In the equilibrium $$t = 0$$
$$ F\Delta T = \frac{E}{c} = \frac{P\Delta T}{c} => *F* = \frac{P}{c} (1) $$
This will be the...
For example: https://www.laserfocusworld.com/test-measurement/research/article/16566273/scientists-develop-saseran-acoustic-laserthat-produces-terahertz-sound-waves
Can these devices produce ionizing radiation?
I understand ultrasound traditionally does not produce ionizing radiation, but I am...
I have a formula for a sphere radiating to the environment where the environment is not at zero temperature. The sphere has a constant heat generated within itself. The formula for the temperature of the sphere under these conditions is:
##T_s = \left( \frac{Q_{gen}}{A_s \sigma \epsilon} +...
Question 1;
a) P=E/t
E=5.796*10^7 J energy produced per day during the summer
However, I am not certain how to calculate the time period, since although this concerns the energy produced per day, the sun does not shine for the entire duration of this 24 hour period. Also, I am unsure of the...
I am currently reading the third edition of Modern Physics by Serway/Moses/Moyer and this quote, in reference to the Compton Effect, seems to conflict with various other online sources I have checked. I understand that the classical description does not give accurate predictions of what actually...
Here is something that struck a note to me, they give the CMB radiation in it's frequency which is in Ghz as the name "microwave" implies and then they also give a temperature in Kelvin.
But how can light aka EM radiation have a temperature? I thought only matter with mass can have a temperature...
Hi All
In discussing another issue it occurred to me the only experiential evidence I know that normal visible light is EM radiation is Faraday Rotation. I strongly suspect we have a lot more these days.
Amusing story. Fermi's wife had a degree in general science that did not cover...
What percentage of the universe’s A) total mass —including dark matter— and B) radiation energy is estimated to reside in:
Inter-galactic space covering i) inter-galactic medium and ii) distinct inter-galactic astronomical objects; and
Galaxies covering iii) inter-stellar gas clouds, iv) stars...
Hi,
the approximate (not accounting for plate size and separation distance) formula for heat flux exchanged via radiation between two parallel plates is:
$$q=\frac{\sigma (T_{1}^{4}-T_{2}^{4})}{\frac{1}{\varepsilon_{1}}+\frac{1}{\varepsilon_{2}}-1}$$ where: ##\sigma## - Stefan-Boltzmann...
Figure from Jackson, the ##0## subscripts indicate incident waves whereas the lack of subscripts indicate the scattered wave.
Figure from Zangwill, the hat ##\hat{e}## vectors are for the incident electric field. We are dealing with unpolarized light so we have two orthogonal polarization...
Hello! I’m currently in the process of earning my bachelors of science in radiation therapy. I plan to get my masters in dosimetry, but I was wondering if anyone know if it was possible for a medical dosimetrist to advance their career by earning their PhD in medical physics. Essentially, I’m...
Hi,
Source: https://en.wikipedia.org/wiki/Second#"Atomic"_second
How were such huge number of periods per second measured originally? Was an instrument such as Michelson interferometer used? I think it was Albert Michelson who invented the interferometer to make calculations of wavelength and...
Hallo, can anybody help me and check if i have the right result:
What is the minimum power P that a point source of radiation (I=8*10^(-7) W/m^2) at a distance of l=10 m from the listener must have in order to still be perceived? (Note: The emitted energy per area can be related to a spherical...
I am grateful for anyone for their time to answer this question.
Some theories predict black holes will evaporate and eventually disappear. From my limited understanding, Hawking's theory predicts that quantum effects near the event horizon of a black hole are responsible for blackbody...
Hi guys, I am confused about the heat transfer mode of between two contacting material, especially in a channel flow.
Obviously, conduction or convection dominate the heat transfer process in the process with low object temperature .
But I am not sure if I have a fluid of 500 Kelvin, flowing...
https://www.thegreenjournal.com/article/S0167-8140(20)30185-7/fulltext
What's the relevant science here ? Would just like to hear a bit more as to whether it holds out any meaningful prospects for treatment of Covid 19.
I've come across this alternative formulation of Planck's Law which links the number density to energy gap
n(E) = \frac{2\pi}{c^2 h^3} \frac{E^2}{exp\big(\frac{E-\mu}{k_BT})-1}
I've tried visualising this relation and I imagine it will look similar to the spectral density relation but I'm just...
The intensity is proportional to the square of the distance between the source and the body and also depends on the angle of incident.
I = The intensity at 0° (Assuming I = some constant)
then I0 = I cos(Theta)
Theta = the angle of incidence.
I want to solve this using trignomentry. Is it...