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Questions tagged [radiation]

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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The law of radioactive decay: explanation of a formula

The law of radioactive decay can be expressed in terms of $\,\tau=1/\lambda$ (average life) as: $$ N(t)=N_0e^{-t/\tau}, \quad \tag{1} $$ Why deriving the (1) I ...
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Radiation pressure at a surface which is perfectly refracting

Radiation pressure at perfectly reflecting surface = 2I/c Radiation pressure at perfectly absorbing surface = I/c What will be the radiation pressure at a perfectly refracting surface? Will it be ...
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Calculating the shielding required to protect against radiation at lunar orbit

I am attempting to calculate the thickness needed to protect the crew inside a space module at the Lunar Orbit with Lithium Hydride from X and Gamma Rays. How would I calculate the thickness of Li-H ...
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What is the formula of operating voltage of GM counter?

In some manuals I found operating voltage formula $$V=V_1+(1/3)(V_2-V_1)$$ and in other manuals $$V=(V_2+V_1)/2.$$ Which formula is correct? If both are correct, then please give the reason.
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Light from an incandescent lamp

In a tungsten filament lamp, electrons travel through a high resistance path,due to which the temperature is increased. Now why does it emit light , is it because of the transitions of electrons from ...
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How are free electrons reincorporated into orbits?

In particular, I'm curious about what happens to beta particles once they lose most of their kinetic energy. As I understand, they'll eventually find their way into orbits of surrounding atoms, but ...
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Possible to detect presence of nuclear bomb? [closed]

Take, for instance, a W-80 nuclear warhead. Does technology exist, say in the form of a satellite or drone, that could detect the warhead's presence (assuming it's not enclosed in some kind of ...
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Experimental beta decay spectrum of free neutrons below 150 keV?

From a pedagogical point of view, beta decay is a really sweet example of relativistic kinematics, and seemingly the best and most natural example to use would be the decay of free neutrons. This is a ...
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Why does a scintillator need to be fast decaying?

I have two scintillators, say, one with a decay time of 1 ns vs. one with 100 ns. All other parameters like light yield, size of crystal, electronics used, source emission rate, are the same for both. ...
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Brehmsstrahlung radiation query - If an electron is constantly being decelerated, how does it emit a photon with a fixed energy?

According to my textbook they simply say an electron is decelerated by a nuclei and this means it loses KE. The difference in KE is given off as a photon. But an electron is always being pulled back ...
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Bremsstrahlung photon energy query

In my textbook they've defined the energy of a photon released by an electron decelerated by a nucleus to be the difference in its KE before and after being decelerated by the nucleus. However I was ...
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Gamma from U238 decay chain

Where can I find detailed information on the gamma background from the U238 decay chain? Edit: Thank you for your replies. I need to find all the branching ratios and extract information of all the ...
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Spectrum of beta decay

I have a very simple question regarding the emission spectrum of a beta decay: Why does the $\beta^+$-spectrum start at $0$ but the $\beta^-$ doesn't? This would mean that there are a bunch of ...
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Scintillator decay time=1000 nsec,does that mean dead time is really high?

What I'm really confused about is, say my scintillator is really slow, and has a decay time of about 1000 nsec. Does that mean, if one neutron is being read by the electronics, for that particular ...
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Has there been any R&D(let alone progress) in the development of gamma voltaic cells?

I ask this because it is my understanding that gamma rays form ion tracks and oxygen radicals when gamma emitting material is immersed in an aqueous solution. Cesium-137 is a very strong gamma ray ...
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Electric quadrupole radiation and supernova core collapse

I have a question when I'm learning the electric quadrupole radiation in E&M. In the radiation zone, the vector potential $\vec{A}(\vec{r},t)$ generated by the current distribution $\vec{J}(\vec{r}...
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Questions regarding germanium detector

Why n+ contact in n type Ge is not several hundred microns? . Why we require both additional p or n type contact? in p type Ge, why we require additional p type junction also? crystal itself should ...
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Radiative Transport Equation scattering phase density probability term question

The development of Radiative Transport Equation has a contribution term called the scattering phase density probability function. It account to scattering events from photons from a different solid ...
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How to derive the allowed beta decay selection rule $\Delta L=0$?

Starting from the beta decay matrix element and Fermi's golden rule how can one show that the matrix element at the leading order vanishes unless $\Delta L=0$?
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Antimatter particle in bananas [duplicate]

I recently came to know that banana produces antimatter. How does this happen and why doesn't the antimatter annihilate as our Earth has matter. I looked for a relevant answer but could not find it.
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Reduced absorption coefficient question

I came across a paper that reads It is noteworthy that for a sample without lateral light propagation in the material, i.e. [reduced scattering] $\mu_s' = \infty$ and [absorption] $\mu_a=0$, ... ...
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Why n+ contact of p type Ge is 700um thick compared to p+ contact of n type Ge only 0.3um?

Whether the reason is as follows? Predominantly HPGe is p type. So compensation of large p type impurity requires more n+ contact. (700um) But n type Ge is made by doping of excess addition of n type ...
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What is the Half-Life of a Large Chunk of Fissile Material?

Uranium-$235$ has a half-life of about $700$ million years and a critical mass of about $52\,$kg. That means if you take a large number of $U$-$235$ atoms, say a $26 \,$kg amount, and put each atom in ...
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Can a neutron decay into a proton + muon (+ muon-neutrino)

Can a neutron, if it has enough kinetic energy, decay like: $ \hspace{0.3cm} n \rightarrow p + \mu^- + \bar{\nu}_\mu $ I assume it's not allowed since it's not on the possible decay modes on the ...
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Microwave Grilles

Bit of an applied physics question here, to do with microwave ovens and the grille in the door through which you can see. My understanding has been that the grille works because the waveform of the ...
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Unit of Spectral Emissive Power

I understand Spectral Emissive Power as the total amount of energy carried by photons having the same wavelength (energy), and it has the unit of (W/m2.um). I could not grasp the physical ...
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can radiation burst provide electrical devices malfunction?

I wonder if a radiation burst create an electrial device malfunction or desactivation. Can radiation create electromagnetic impulse ?
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How does the heat capacity of an object come into play in thermal radiation?

So say there's a cube in space acting as a blackbody. Each side is 2 metres. Initial cube temperature is 400 Kelvin. Mass is 15 kg. Say the heat capacity is 500 J/kgK. How would that affect thermal ...
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Radiation heat exchange between grey bodies formula explanation

Given two grey bodies (heat emissivity = heat absorbtion, emissivity($\lambda$) = constant = $\epsilon$ foreach $\lambda$) in a vacuum, how much power P would the hotter transmit to the coldest? S1, ...
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How does particles move in waves? radiation?

I'm reading about particles for a project and had a question. I read that particles don't move forward in a wave, the simply oscillate up and down, and that gives it the wave look. But if they don't ...
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How do I get energy distribution of radiation (Planck's Law) in terms of frequency?

I have $$u(\lambda) d\lambda = \frac{8\pi hc\lambda^{-5}}{e^{hc/\lambda kT} - 1}d\lambda$$ I want this in terms of frequency. I can start with $\lambda =c/f$ but I will end up with $u(c/f)$ rather ...
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Would plasma that is as electron dense as lead be a better shield than lead against gamma radiation?

Imagine you somehow managed to maintain a body of plasma which had the same electron density as an identical volume of lead or other heavy metal. (Suppose you ionized lead.) Would it be a better gamma ...
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Will a black body placed somewhere around the Sun obtain (eventually) the same temperature as the Sun?

Suppose we look (above the Earth's atmosphere) at the wavelength ($=\frac c f)$ spectrum emitted by the Sun: This shows that the Sun is approximately a black body with a temperature of about $5525(K)....
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Can't see any traces of particles in my Wilson chamber without radioactive material

I am doing an essay about particle physics and I need some help. I am comparing the results in a Wilsonchamber with and without a radioactive material present. I were able to see a lot of traces from ...
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Determination of Dead time of a Geiger Muller counter using the two source method

While determining the dead time of a GM counter using the two source method, why do we ensure that only two sources are placed in the counter at all times i.e. while determining the counts when both ...
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Forming a Neutron Star: inverse $\beta^-$ decay or electron capture?

There are three different kinds of beta decays: $\beta^-$: n $\rightarrow$ p + e$^-$ + $\overline{\nu}_{e^-}$ $\beta^+$: p $\rightarrow$ n + e$^+$ + $\nu_{e}$ electron capture: p + e$^-$ $\rightarrow$...
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How would a fast-moving atom interact with a body? [closed]

I found this question on Quora: https://www.quora.com/Can-you-theoretically-shoot-an-atom-fast-enough-to-kill-its-target I think the Quora answer is good but incomplete, and it got me wondering what ...
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1 Picocuries per liter is how many millirems per year? [duplicate]

How can you calculate how many millirems of radioactive particles occur per year? The measurements don't seem to match up with radon testing information. 333 millirems in a year not accounting for ...
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Satellite radiance measurements in spectral regions

Q: A satellite measures longwave radiation emerging from a planet with uniform surface temperature T1 and uniform atmospheric temperature T2. What values of radiance does the satellite measure in the ...
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Intuition for why matter dominated expansion is faster than radiation domination?

In a matter dominated universe $a_{\rm mat.}(t)\sim t^{2/3}$, while in a radiation dominated universe, $a(t)_{\rm rad.}\sim t^{1/2}$. Therefore, a matter dominated universe is expanding more quickly, ...
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How are solar sails maneuvered by sunlight? Are they pushed or pulled?

On 20 May, 2010, Japan launched IKAROS probe with primary propulsion by a solar sail. If the radiation pressure, that helps the sail to move, comes from the sun, then shouldn't it be pushed away from ...
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Is it possible for antimatter to be created from a nucleus of regular matter decaying?

I have a limited understanding of nuclear reactions. I know of the decay in which a positron is emitted from a nucleus and a proton is converted back into a neutron. There is also another type of ...
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What is the rotation profile for radiative zone of Sun - Instability and convection?

I am exercising on Stellar Physics topics and in particular the questions below: 1) First of all on the rotation profile for the radiative zone: I know that unlike the convective zone, where the ...
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Do materials approach black body behavior as temperature increases

I have emittance curves of a material (that cannot be shared) that show an increase in emittance values over a wide wavelength range. As the temperature increases, the value for emittance increases, ...
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1answer
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What is the incident power of the sun for different parts of the U.S over time?

I have seen number as low as $200\ \text{W}/\text{m}^2$ to $1000 \text{W}/\text{m}^2$. I'm in California and looking for information on how much power my solar panels will pick up. I have $4100\ \...
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When you cook food in a microwave oven, why does't the plate get cooked? [closed]

When you cook food in a microwave oven, why doesn't the plate get cooked?
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How is the Solid in Oven centre Hottest [closed]

When a solid (any material) is placed in an oven and heated, the theory of radiation works I guess. How it the centre of the solid the hottest and not the surface of the Solid which actually receives ...
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Synchrotron Radiation for Electrons, Protons and Ions

I understand the principle of synchrotron radiation in saying that , when a charged particle gyrates around some magnetic field line it emits energy in the form of photons. However I can't ...
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Nuclear reaction – What is the asterisk an indication of?

I've been observing the two-step decay of iodine-131 and can't quite determine what the asterisk above Xenon-131 indicates. I'm currently unsure as to what precisely the superscript asterisk on Xenon ...
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Experimental evidences satisfying charged particle emits radiation in gravitational field

Is there any experimental evidence exist that a charged particle at rest in gravitational field emit radiation and charged particle in free fall don't emit radiation ( According to equivalence ...