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.
1,628 questions
0
votes
0
answers
50
views
Why should the specific intensity of a source be left unchanged while imaging through a lens?
so I was going through R. Rutten's notes on radiative transfer, where he poses a question about the specific intensity of a light source that is placed at the focus of a lens.
A lamp radiates with ...
- 11
4
votes
1
answer
95
views
Does the velocity of an object moving towards a beta or alpha particle increase the impact force?
Please excuse my limited understanding of physics, but I need help clarifying an issue I have been struggling with. NASA explains that the Apollo crews reduced their exposure to Van Allen Belt ...
- 439
1
vote
0
answers
41
views
Surface and atmosphere radiative exchange
When considering the radiative exchange between the Earth’s surface (with high broadband opacity and ε~0.95), and the band emissions of the atmosphere, with an average of around 10% transmission, we ...
- 57
3
votes
0
answers
102
views
It is really true that we still know virtually nothing about $^{248}\rm{Bk}$ after 60 years?
Back in 1965, the article The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248 reported an isomer of $^{248}\rm{Bk}$ (now listed to have a spin of $6^+$). The article stated ...
- 247
-1
votes
1
answer
125
views
What astrophysical or artificial light sources provide the highest usable irradiance at the Solar Gravitational Lens focal line (∼550–1000 AU)?
The Solar Gravitational Lens (SGL) concentrates light from distant sources into a narrow diffraction pattern along its focal line, starting at ~550 AU. The central PSF contains extremely high ...
- 2,127
0
votes
1
answer
109
views
Is there a periodic table showing the radioactivity of elements in their natural isotoic ratios?
In something like decays per second because a stable elements doesn't really have a half life
- 107
1
vote
1
answer
160
views
Why a particle (specifically lepton) decays?
This is a sequel of my question. For particles with structure, it wouldn’t be strange for them to decay due to unstable structure and various reasons. But for leptons, such as the muon, it's almost ...
- 189
3
votes
3
answers
2k
views
Will gases contained inside a box eventually reach zero temperature?
Suppose I have some amount of gas inside an isolated box.
As the gas molecules continue colliding with box wall and each other, there will be a loss of energy due to these collisions.
So, will over ...
- 423
4
votes
1
answer
301
views
Is there a limit where the inverse square law does not apply?
Struggling to wrap my head around making estimates of neutron dose rates. I have an AmBe neutron source, surrounded by a neutron shield with a complex shape (due to engineering considerations). It is (...
1
vote
1
answer
132
views
Can Ultraviolet Light Penetrate Fiberglass?
I was installing a fiberglass camper shell on my pickup on a sunny day. When I climbed in the back to install the bolts and secure the shell to the truck, of course it was shaded from the sun. After a ...
- 113
1
vote
1
answer
123
views
Which Dosimetry Approach is Correct?
I have been studying gamma and X-ray irradiation for sterilisation purposes. Dosimetry plays a crucial role in this concept. The unit for dose it in Gray (Gy) which is,
$$\text{Dose (Gy)} = \dfrac{\...
1
vote
1
answer
173
views
How to reconcile photons and different aspects of electromagnetic fields? [closed]
I am learning about fields and EM waves, and there is something I find trouble reconciling. I am told of the field theory of electromagnetics, but then I also read fields are simply made of photons? ...
0
votes
1
answer
126
views
Intuitive explanation for the combinatorial factor present in $d\Gamma$ (diff. decay rate)
The formula for the differential decay rate of an unstable particle that decays into $n$ particles (as given in Wikipedia and other sources) is:
$$d\Gamma_n=\frac{S|\mathcal{M}|^2}{2M} d\Phi_n(P;p_1,...
- 2,076
4
votes
1
answer
271
views
Deriving the power density of Johnson's noise (as in Feynman's Lecture I.41)
This is a question related to sections 41.1 41.2 and 41.3 of the Feynman Lectures on Physics (vol I). Below, I will summarize the content of section 41.1 and 41.2 and then report what is unclear to me ...
- 289
0
votes
3
answers
230
views
What is my geiger counter picking up from this neon discharge lamp?
This is just a mini tesla coil exciting an Eisco neon discharge lamp. The detector is a MightyOhm geiger ++ which detects beta and gamma radiation. I'm recording 30-60 CPM just with background ...
