# Tagged Questions

Radiation is a process in which energetic particles or energetic waves travel through a medium or space. The particles or waves radiate (i.e., travel outward in all directions) from a source.

82 views

### What minimum energy is required to create tracks in a cloud chamber?

What is the minimum ionizing radiation required for that? I am currently living in Fukushima prefecture and I was wondering if let`s say a flower from my yard that emits 1 pSv will create visible ...
166 views

I'm running out of places to look (lots of Googling, SE, [articles and books are too specific and never give a good overview]), and yet I am still unsure about how exactly radiation can degrade ...
35 views

### How to calculate material depth at which penetrating radiation direction becomes randomized?

Consider a very light particle impinging on a material composed of atoms which are effectively infinitely heavy (e.g., because they are bound together and stiff). If the scattering with nuclei is ...
73 views

### Klein-Nishina for estimating X-ray cross section

I'm looking at interaction probability for X-rays with water and DNA, and recently have starting reading up on the Klein-Nishina identities for differential cross section. When integrated over all ...
33 views

### Understanding view-/formfactor for radiation with a specific example

There is radiation coming from a point source (black body). How much of the total emitted energy (from the point source) hits a spherical surface given by $\phi = 0 - \pi$ and $\theta = 0 - \pi/2$? ...
86 views

### Alternatives to the neutrino in the beta spectrum?

It is well known that the neutrino appeared to explain the power distribution in the beta decay spectrum. (see PSE) What other explanations candidates were available? It is stated that the ...
29 views

I am working through a derivation of the spectral energy density in a 1d cavity. The derivation says that the number of modes (per unit volume) in a frequency interval $dv$ is given by: $$g(\nu)d\nu =... 1answer 85 views ### Can someone explain the radioactive decay of that would happen over time to a 1 cubic decimeter block of plutonium? [closed] I just saw an article talking about naturally occurring plutonium on Earth and it said that some [or many or some other purposefully ambiguous statement] people think this element could [another good ... 3answers 607 views ### How do particles “know” when to decay? So, as I understand it, in a substance that is made of radioactive elements, the half-life tells us how long until the half of those atoms decay into their next atom [is there a name for that: the ... 1answer 54 views ### Measured temperature (thermometre set to emissivity of 1) of smooth surface too high or to low? We want to measure the temperature of a smooth flat surface with a thermometre based on absorption of thermal rays. The emissivity setting of the thermometre is set to 1 (same as a black surface), ... 3answers 3k views ### Is heat from a stovetop, transfered through convection, radiation or conduction? It doesn't appear to be convection, as there are no moving objects (or are there); probably not radiation (?), so it is conduction? I really don't know much about heat transfer and thermodynamics, ... 3answers 924 views ### How do we know that the cesium-beam frequency used in atomic clocks is always the same? Atomic clocks use cesium-beam frequency to determine the length of a second. This has shown that the period of orbit of the earth is decreasing. But what experiment showed that cesium-beam's period ... 2answers 5k views ### Why doesn't the evening/morning sun feel much hotter on your face? I understand that places on the Earth's surface get hotter in summer, and in the middle of the day rather than morning or evening, because the surface of the Earth is presented 'face-on' to the Sun at ... 2answers 294 views ### By what maximum amount can we concentrate sunlight? This refers to a previous question re: Solar Cell Systems and as part of the answer the statement: If we concentrated sunlight to [the] maximum amount 42600× was given. My questions are: By what ... 1answer 360 views ### Increasing the efficiency of solar cell systems As far as I know, there are currently two main approaches to utilising solar radiation for maximum energy conversion to electricity. These are either direct conversion to electricity, using ... 1answer 147 views ### What is the difference between zero background radiation and field background radiation in Nuclear Physics measurements? Can someone please explain the difference between these two terms (Zero Background Radiation and Field Background Radiation) used in radiometric prospecting measurements? 1answer 46 views ### Carbon 14 disintegration When \beta^- disintegration happens to a Carbon 14 atom, a neutron "turns into" a proton, and an electron is emitted. Therefore the result of the disintegration is a Nitrogen atom plus an electron (... 1answer 180 views ### What is the energy threshhold to produce Cherenkov radiation? I am in a nuclear course right now and am getting some misleading information from different sources. I am trying to figure out what the minimum total energy is that a proton must have in order to ... 2answers 121 views ### How does “contamination” through (radioactive) radiation work? Physically, what does it mean when people or objects are contaminated with radiation? Is it because they actually carrying heavy metal particles? 1answer 408 views ### Surfaces that reflect UV rays I've been trying to research what surfaces reflect UV rays for the past day but it's been difficult coming up with definitive answers. So far what I've found is that surfaces that reflect visible ... 1answer 34 views ### Does the W boson in beta decay affect the gravity generated by the system? During beta decay we now know a heavy W boson gets involved temporarily. Would this potentially impact the gravitational field generated by the system as a whole? It doesn't seem like it should. Just ... 1answer 2k views ### Relationship between temperature and wavelength? I am investigating the relationship between wavelength and temperature. As seen the figure below of Planks law What is the relationship between the lambda(max) and Temperature? or in simpler ... 2answers 179 views ### beta minus decay: expression for maximum electron energy I'm having some trouble finding an expression for the maximum electron energy in beta minus decay. In the frame where the neutron is initially at rest, conservation of momentum reads:$$\vec{p}_p+\...
57 views

I'm running an experiment in gamma-ray imaging (although the main emission from the decay of Am-241 is ~60keV, so much more in the range of x-rays). I'm curious as to the sort of sources that would ...
58 views

There are plenty of lists of sources of general background radiation, but can anyone reduce that list to the major contributing sources purely for background gamma radiation (specifically low energy, ...
47 views

### What process happens in an IT nuclear decay?

I've been researching medical isotopes and alot of them decay by an IT path. Does anyone know what IT stands for? And what physical process is happening? Example: http://www.nndc.bnl.gov/nudat2/...
156 views

### Why the CMB has not been dispersed so far?

Imagine you have a box of black body radiation. What happens if you open the box for a long time? It becomes dispersed and no radiation remains in the box. Now, apply this example to the Cosmic ...
4k views

### Why do microwave ovens use radiation with such long wavelength?

According to Wikipedia: Consumer ovens usually use 2.45 gigahertz (GHz)—a wavelength of 12.2 centimetres (4.80 in). Typically, I put the dish inside the oven in its center. I suspect most ...
1k views

### Lethal dose of Gy's (Grays)

The unit Gray has the dimensions $\text{J/kg}$. I've read, that a dose of about 3-5 Gy's could kill a person within a few weeks - or at least that's usually the case. But I'm not really understanding ...
49 views

### How do experimental physicists know the decay path of transuranium elements ahead of time?

I have been watching (and enjoying) Dr. Poliakoff's YouTube videos on the synthesis of transuranium elements like Roentgenium and Copernicium, which decay so quickly that they are identified (if I ...
97 views

394 views

### How would the explosion from a Pure Fusion Bomb differ from the explosion from a Fission Nuclear Bomb?

Suppose we have the technology to create high enough temperatures and pressures inside a confined space to fuse together deuterium and tritium, and create a Pure Fusion Bomb. How would the explosion ...
740 views

### How hot is Plutonium-238 in Radioisotope Thermoelectric Generators (RTGs)?

As I understand it, Plutonium-238 is used to provide power through heat generation in radioisotope thermoelectric generators. My question is... how hot is a pellet of Plutonium-238? Does the heat ...
1k views

### Does tin foil keep heat out?

For example, if i were mailing a box of chocolates and lined the inside of the box with foil, then wrapped the chocolate in bubble wrap and placed it inside the foil lined box, would the box heat up ...
203 views

### pGRE question on natural line width

The lifetime for the $2p \rightarrow 1s$ transition in hydrogen is $1.6 \times 10^{-9}$ s. The natural line width for the radiation emitted during the transition is approximately... Their solution: ...
113 views

### Reactive near field for Wireless Power Transfer (WPT)

In literature it is stated that in reactive near field using high-Q coils in resonance the efficiency does not depend on coupling (ie. distance) and that coupling only has influence on rate of energy ...
821 views

### Deriving Gamow factor for potential with effective centrifugal potential term

I am looking at deriving an expression for the Gamow factor for $\alpha$-decay. I understand that the potential is the sum of the nuclear, electric and effective potentials: V(r) = V_N(r)+V_c(r) +\...
46 views

### What is a high brilliance X-Ray and how is one created

I just found this term being used in a Stanford Engineering year in review 2013-2014 "X-rays illuminate path to more efficient fuel cells" that cited this work. Never heard the term before and I came ...
206 views

### We don't know when a nucleus will decay. Then how can find its half life? [duplicate]

I mean how can we say that in 5730 years, 1/2 the no. of C14 nucleus will decay because in reality we don't know when a particular nucleus will decay