qftme

529 reputation

312

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	location	London, United Kingdom
	age	28
visits	member for	2 years, 3 months
	seen	Dec 3 '12 at 15:05
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Phd student

	529 reputation	bio	website		visits	member for	2 years, 3 months
312 badges		location	London, United Kingdom		seen	Dec 3 '12 at 15:05

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2d	awarded	Popular Question
Jan 31	awarded	Yearling
Nov 30	awarded	Popular Question
Nov 29	awarded	Nice Question
Feb 23	comment	Cosmic radiation cutoff at LOW energies? Below 1GeV particles aren't generally considered relativistic and therefore, when they bombard our atmosphere from outer-space, they're just not normally refered to as cosmic rays. Furthmore, sub-GeV particles would very quickly thermalise in our atmosphere (Ie exhibit Brownian motion) and therefore retain no information about from where they came.
Feb 23	comment	Cosmic radiation cutoff at LOW energies? From where did you here there was a low energy cut-off? Technically, there isn't. Stable particles (alphas, protons, neutrinos etc) can have arbitarily low energies. Of course there comes a point when either; we would tend not to refer to them as cosmic rays (most would be solar wind for example), or when detector technolgy prevents us from seeing them. However, these don't really constitute as a 'cut-off' in the traditional sense of the word.
Feb 22	comment	Cerenkov light - a practical calculation @zephyr, could you perhaps type up your calculation into an answer? Allbeit approximate, I think it will be sufficient for my purposes and will therefore duly accept it.
Feb 20	comment	Cerenkov light - a practical calculation Isn't it okay to assume that the muon would be travelling at $c$ throughout it's passage through the glass? It is only 10cm afterall. For a $5keV$ muon: $1-v/c=2.4\times10^{-5}$. Either way, my attempt at the calculation gave $4\times10^{-47}J$ which I really don't think is correct. Basically I'm still stuck :(
Feb 20	comment	Cerenkov light - a practical calculation Hi zephr. Of course your right if the integral were carried out over the full range of frequencies. In practice however, I'll be using something like this[1] to detect ring patterns and it is sensitive only to wavelengths in the range 300-650nm. [1]: sales.hamamatsu.com/index.php?id=13199716&language=2&;
Feb 20	asked	Cerenkov light - a practical calculation
Jan 31	awarded	Yearling
Oct 11	awarded	Organizer
Oct 11	revised	Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$? Created new tag
Oct 11	suggested	suggested edit on Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$?
Oct 11	comment	Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$? Hi @dmckee: the equations should read $s=ut+\frac{at^2}{2}$, $s=\frac{(v+u)t}{2}$, $v=u+at$, and $v^2=u^2+2as$. Or at least they are the ones I was forced to remember some 10 years ago ;-)
Oct 11	answered	How can I explain why the weak nuclear interaction between individual nucleons is 'weak'?
Aug 4	comment	Particle physics plots Hi Jim: if you search through some of the older posts of this blog you'll find many lucid and pedagogical explanations of particle physics graphs: blog.vixra.org
Jul 29	comment	What does scalar phi represent in spacetime? Can't decide whether I like the clarity or the humour more in this answer: +1 ;)
Jul 28	accepted	Roughly how many atoms thick is the layer of graphite left by a pencil writing on paper?
Jul 28	comment	Roughly how many atoms thick is the layer of graphite left by a pencil writing on paper? Tim: In light of your above comment defending your answer I have decided it warranted my accepting it. Thanks also to @TheSheepMan for his experimental perspective.