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.

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How to measure the wavelengths of ultraviolet lines in the hydrogen spectrum?

how to measure the wavelengths of ultraviolet radiation isn't it invisible? it's possible to measure visible radiation but how to measure invisible radiation?
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72 views

How did Lyman discover his series?

How did Lyman discover his series in hydrogen atom? How did he know that the final energy level is the first level and not the second or the third or etc.? Or how did the other scientists know which ...
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1answer
69 views

Deriving Rabi rotation matrix

I want to understand where the matrix: $$ \left|\psi(t)\right> = \binom{a(t)}{b(t)} = \begin{bmatrix} cos(\Omega t/2)&-ie^{i\phi_L t}sin(\Omega t/2) \\ -ie^{-i\phi_L t}sin(\Omega t/2) & ...
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How can we detect cosmic background radiation?

From what I understand, CMB is the left over radiation from the Big Bang. As all matter, including the Earth, was made during the Big Bang and then as the universe expanded that matter/energy got ...
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1answer
70 views

Blackbody radiation and Spectral Lines [duplicate]

Blackbody radiation is thermal radiation from a hot object emitted over a continuous range of wavelengths. But why are spectral lines, lines (i.e., you only get certain wavelengths when an element is ...
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1answer
36 views

Alpha scattering, observations and conclusions

For Rutherford's alpha scattering experiment where he fired alpha particles at a thin sheet of metal to determine the size of the nucleus, please can someone give me the direct link between his ...
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27 views

Rutherfords alpha scattering conclutions? [duplicate]

Please can some one give me rutherfords observations and his conclutions from each onbservation, I have looked in text books but they only give them sepratly with no direct link betweeen which ...
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1answer
118 views

Calculating the number of quanta emitted as Cherenkov radiation in a wavelength interval dl?

This website gives an equation for it http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/cherenkov.html It appears as plaintext but this is what I believe it is parsed: $n = \dfrac{dl 2πα ...
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1answer
110 views

Energy balance for beta decay of cobalt-60

I am confused by a simple fact about the $\beta^{-}$ decay of ${}^{60}{\rm Co}$ nucleus. According to Wikipedia, the most likely decay branch is to an excited state of ${}^{60}{\rm Ni}$, see the ...
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27 views

How to compute radiated power from known instantaneous potential distribution

Friend of mine has a device that has an oscillating electric potential and he wants to know how much power it radiates. He can simulate the instantaneous electric potential using a software package, ...
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4answers
224 views

Do photons make the universe expand?

I have a problem understanding the ideas behind a basic assumption of cosmology. The Friedmann equations follow from Newtonian mechanics and conservation of Energy-momentum $(E_{kin}+E_{pot}=E_{tot})$ ...
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10 views

Dangerous levels of ozone from combined UVB lamps?

I have a reptil UVB lamp in my room, and a de-humidifier that uses a UV lamp to clean the air passing through it. Honestly since I got it working (the lamp was dead at first) my room is mold free. I ...
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46 views

Algorithm for distribution of radiation

Unstable atomic nuclei will spontaneously decompose to form nuclei with a higher stability. What is the algorithm for deciding what sort of it is? (alpha, beta, gamma, etc. Also, given that alpha and ...
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1answer
74 views

Use of fission products for electricity generation

Why can't we use fissions products for electricity production ? As far has I know fissions products from current nuclear power plants create enough 'waste' heat to boil water; and temperature ...
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3answers
120 views

What is radiation(in simple words)? [closed]

I am a student who is interested in scientific facts. I want a simple definition for radiation. Neither too scientific, nor too simple.
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1answer
58 views

Characteristic x-ray in energy spectrum

Context: Monte Carlo simulation of a linear accelerator photon beam. The energy spectrum for photons as calculated from the phase space files found in here has a peak somewhere near ...
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4answers
211 views

Detecting radiation from tritium keychain

I am measuring radiation from 6 tritium glow keychains. Usual gamma detector does not detect anything (this is expected), but on beta detector with thin window I am getting about 5 counts per second. ...
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2answers
149 views

Why doesn't diamond glow when hot?

In an answer to this SE question, the respondent explains that heating a perfect diamond will not cause it to glow with thermal blackbody radiation. I don't quite follow his explanation. I think it ...
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3answers
4k views

Is it possible to avoid the radiation that caused the American flag turned into white on the Moon? [closed]

While lunar images have proven that the American flags planted during the Apollo missions are still standing on the moon, lunar scientists have now said that they probably no longer hold the iconic ...
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2answers
365 views

Why doesn't a nuclear fuel pool become irradiated?

Why doesn't the volume of water in a nuclear fuel pool become irradiated? Why wouldn't the water around the pool become radioactive and circulate around making the whole thing deadly? My question ...
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1answer
71 views

interior surface of furnaces

For industrial furnaces, in order to improve radiation heat transfer and save energy, some people say applying a high emissivity coating on to the interior surface of a furnace will do, while some ...
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1answer
147 views

Soft Bremsstrahlung: why $\hat{k}\cdot\mathbf{v}= \mathbf{v}'\cdot\mathbf{v}$?

On page 181 in Peskin & Schroeder they say that we consider the integral (intensity) $$\tag{1}\mathcal{I}(\mathbf{v},\mathbf{v}') = ...
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3answers
405 views

is an electron gun dangerous?

Is an electron gun dangerous & what would be the repercussions to human tissue? If I were to do a DIY electron gun and put my hand in the beam would I regret it?
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1answer
110 views

How much power would a space craft's magnetic shield require? [closed]

I've read over the decades that a magnetic shield might protect a spacecraft from cosmic radiation. Its a fascinating idea that might only be theory or science fiction at the moment. In regards to ...
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348 views

The problem of self-force on point charges

Allow me to preface this by stating that I am a high school student interested in physics and self-studying using a variety of resources, both on- and off-line, primarily GSU's HyperPhysics website, ...
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29 views

Bystander effect: last works?

Do you know the last works about Bystander Effect on cells caused by radiations? I have found research papers until 2004.
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0answers
153 views

Effects of microwaves on optical properties of human eye [closed]

I have read a long series of paragraphs on wiki. Previously I thought that microwaves are not harmful to living beings but Wiki does not claim this explicitly. while doing an experiment in my college ...
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1answer
61 views

How many radiotherapy sessions would it take to boil one cup of water? [closed]

Context: Gray (Gy) is a unit dose used in radiotherapy. It is defined as the absorbed energy of 1J per kilogram of matter. There is a wide misconception that ionizing radiation acts by heating ...
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53 views

What is the nature of energy? [duplicate]

In science fiction adventures, spacecraft are sometime equipped with "energy beams", i.e. devices that can project pure energy unassociated with matter. Is this possible? Is energy a "thing" in the ...
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2answers
46 views

Do molecular bounded systems shield or reduce neutron cross-sections?

When talking about neutron cross-sections, literature is usually investigating isolated cases of Neutron + Atom. Here, the abundance of hydrogen is dominating neutron fluxes through material. I ...
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1answer
49 views

$α$-decay and electron

I'm a Web developer and I'm working on a physic interactive Web page to represent how atoms interact. I'm reading information about α-decay and here is what I understand. Let's say we have a isotope ...
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2answers
40 views

Measuring radon level

In theory what are the techniques used to measure the levels of radon in air? On which principle/law do they rely?
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3answers
121 views

light beams of the sun [closed]

We receive sunlight on earth surface. What type of light beams are these? Random/Parallel/Converging/Diverging I think it should be Diverging as Sun is radiating these beams away. But in one ...
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2answers
162 views

Does blackbody radiation work like this?

In a blackbody object the photons are reflected back and forward. If I heat up the the blackbody object with microwaves or other types of photons the electrons in the wall would vibrate. When the ...
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2answers
315 views

Measuring background radiation

We tried to measure background radiation using a geiger counter for a experiment at school. The meter showed $0.12$-$0.21$ microSv/h during the day averaging at about $0.14$ mcSv/h. As we tried to ...
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1answer
88 views

Is terahertz radiation new?

Regarding the future applications of terahertz technology, I thought we already knew the entire electromagnetic spectrum. In fact we do not, terahertz lies between microwaves and infrared radiation. ...
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51 views

Beta-decay of the neutron

Could you please tell me, where can I find a straightforward calculation with all details of beta-decay of neutron? To find the amplitude and to square it is difficult, but possible. The main problem ...
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2answers
77 views

What causes different decays?

Nuclei spontaneously decay according to a certain decay rate. There are however different kinds of decay, alpha, beta, gamma... What causes then the nuclei, when they decay, to do so in one way of ...
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1answer
90 views

Trying to turn a nonlinear differential equation into a linear one

The problem I have today is to determine the differential equation for a square fin protruding from a wall that experiences surface to ambient radiation and has an internal heat generation of $\dot q$ ...
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1answer
160 views

What determines the distribution of the energy between the beta-particle and the neutrino in beta decay?

When beta-decay occurs an electron or a positron is emitted along a neutrino or an antineutrino. The energy spectrum of the beta particles is continuous because, as I read, the energy is shared ...
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0answers
12 views

What are the coefficients of the Geiger-Nutall law dependent on?

The Geiger-Nutall law for alpha-particles predicts a linear relationship between the logarithm of the decay rate and the energy of the particle, and I've observed that in ln(decay rate) / (energy) ...
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1answer
410 views

Where is radiation density in the Planck 2013 results?

I've been looking at the Planck 2013 cosmological parameters paper, trying to update my toy cosmology simulator with the most recent data. Most of the interesting values such as $H_0$, $\Omega_m$, ...
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25 views

Origin of the names for the decay chains

Is there any reason for the names of the decay chains? As shown in this chart (larger version here): only the Thorium chain starts on an isotope of the element it takes its name from, and it can ...
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3answers
143 views

Radiation at plate of vacuum tube

Say you have a vacuum tube, such as the kind used in old amplifiers, wherein electrons are accelerated from the cathode to the anode through an electric field. Presuming, for the sake of argument, ...
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221 views

How Does Lead Block Radiation

How is it that lead can block radiation, and things are lead lined. In the Indiana Jones 4 movie he climbs inside a lead-lined fridge and he somehow survives the blast and radiation?
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“Single-shot” Heat engine efficiency limits

The sun is 5778K and Earth is ~290K. Using the sun as the hot reservoir and earth as a cold reservoir we get 95% Carnot efficiency. However, the solar power efficiency limit is only 86%, see: ...
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88 views

Is it possible to calculate the half-life of a nucleus?

Is it possible to calculate theoretically the half life of a nucleus (how?) or they are all known through measurements? As an example how do you calculate the half life of Carbon-14?
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3answers
252 views

What does the decay constant mean?

In my curriculum, the decay constant is "the probability of decay per unit time" To me, this seems non-sensical, as the decay constant can be greater than one, which would imply that a particle has a ...
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3answers
313 views

Why don't we use beta radiation for making electricity?

Why don't we use beta radiation to make our electricity? Since it is an electron being released/made, it would make sense to try and capture it. But, we obviously don't so. What am I missing in my ...
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343 views

Does brightness of the light remains constant with the variation of the distance with respect to the source in vaccum?

I have this question going in my mind from many days, i.e why brightness of light emitted from any light source around us decreases with distance? The brightness of light from tube light, streetlight, ...