Radiation Definition and 1000 Threads

Although problem says sketch, what I really want is the formulae by θ for the radiation. After trying this for a while I cheated and looked at the solution. I still can't figure out the steps on how to get to the solution. the answer is: What I tried: I'll assume that the intensity from a...

Hi I am currently taking a physics course and studying black body radiation.I have already seen a good number of books , but I have a lot of unanswered questions. -What does the black body radiation, which is approximately the radiation of the sun, has to do with standing waves inside a cavity...

Hello, So I was reading about Hawking radiation and I read a QFT interpretation of it. It went something like this: A vacuum contains virtual particles (vacuum energy), which in qft can be described as waves that are out of phase and cancel each other out (matter and antimatter). I a black...

Why are smoke detectors with Americium exempt from leak testing when there are ones in older houses maybe 30 years old and one needs to open them up to change the battery. Surely the Americium could leak out over time from the ionisation chamber?

What is the threshold energy (or frequency) required for an electromagnetic field to transition from a near field to become self propagating (EMR), far field? (If I'm using the right definitions to ask the question correctly). Is this constant or are there other details needed to calculate this?

I would like to find out please what is the preferred instrument to leak test very low levels of leaks of Americium, say in school sources. I mean an instrument which could measure leaks of 0.0005 microcuries. There are so many instruments. Some people say to measure the gamma emissions, others...

I was wondering how many visible photons humans emit in a day. I did all the calculations with the Planck's Law (it's quite easy, because in the visible spectrum and for temperatures above 0 degrees the exponential term is much larger than one, and the "-1" can be taken out of the integral...

I have encountered two (?) definitions of the electric quadrupole moment. They are: $$Q_{ij}=\frac{1}{2}\int \rho(\vec{x}')x'_i x'_j\,\mathrm{d}^3x'$$ and $$Q_{ij}=\int (3x'_i x'_j-\delta_{ij}x'^2)\rho(\vec{x}')\,\mathrm{d}^3x'$$ I am trying to study radiation arising from the electric...

Theoretically could an observer in a black hole perceive hawking radiation escaping the black hole as a black hole within the black hole? Also if so maybe that black hole could produce a radiation similar to or related to hawking radiation (Making a strange entangled system for conservation of...

I've had this question rattling around in my head for some time now, but I think it'd be easier asking it here than reading several books to gather sufficient information to answer it: I've heard that, in general, the detonation of enough nuclear weapons on a short enough time scale will cause...

Several sources of background radiation include; Radon gas from soil, rocks and building minerals; since radon is produced by the decay of uranium ore present in certain rocks e.g. granite. On Earth, approximately 42-51% of background radiation is the result of naturally radioactive gases like...

I'm wondering what the relationship between blackbody radiation and spontaneous emission is. As far as I know, there are three sources of EM radiation - thermal radiation, oscillating dipole (multipole?), and LASER. And it seems like light emission from an atom can be separated into two...

Hi, Never done much cosmology but reading around I have found several sources saying the early universe (pre roughly 300,000 years) the early universe was full of gamma radiation. Since the universe has expanded this gamma radiation has been red shifted into the microwave region. Other sources...

I know that the Sun is at a very far distance from the lens, so I assume the rays are parallel and the image is formed at the focus (500mm away from the centre of the lens). How do I calculate the diameter of the image? The hint to solving this problem says that "The angular diameters of...

So using the above equation, e=dQ/dt / (A*5.67E-8*303.8^4) The surface area of a sphere is 4(pi)r^2 and I get 136.8478 m^2. dQ/dt would be the net radiation (I think? Its in the correct units), 1074W. Plugging everything in I get 0.01625, but the answer is 0.0524. Now as I was writing this I...

Recently when cleaning, I opened the cover of our ionisation smoke detector and as I was touching all around the inside of the smoke detector with my bare hands and most importantly including all the sides of the ionization chamber with the radiation symbol on it which contains the radiation...

I don't understand how this can be solved. The official solution was: F=\sigma*T^4 E=F*4\pi R^2*60*60 This doesn't make sense to me, as it seems to imply that the energy that the black body radiates depends on the radius of the shell. For a very large shell the body will reflect...

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! ☺

<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.

What is the difference between peak dose 100 kRads (Si) and peak dose rate 10 x 10^12 Rads (Si)/s? Can someone explain?

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...

What are the reasons X-ray vacuum tubes could not be replaced by solid state alternatives?

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...