RE: blue flash and criticality

["Bradshaw, Keith" <Keith.Bradshaw@nnc.co.uk>]

Isn't Cerenkov radiation directional?

My limited understanding of this is that the Cerenkov radiation is emitted
in a cone along the particle path, the angle of which depends on the
particle velocity and refractive index of the medium.  In other words,
irrespective of any Doppler shift, if you were behind the source and
shielded from it, you would not see the Cerenkov radiation, because the
particles are heading away from you, and the Cerenkov radiation is at some
angle to that.  You would have to be at some angle to the line of flight to
observe it.  It might be difficult or impossible to to be both at the
optimum angle AND fully shielded from the critical mass.

Personal views only

keith.bradshaw@nnc.co.uk


	>>My question now is, IF, you had a camera, and the source of
criticality 
> >>was shielded from the camera's angle, in other words that the source was
> 
> >>going away from the camera instead of at it, and you you were able to 
> >>establish the original spectrum from long distance face on photography, 
> >>would it be red shifted going away?
> 
	>....from my limited understanding of Cherenkov radiation I believe
the 
	>answer to your question to be..No.  Cherenkov light is not the
result of a 
	>doppler shift in the emitted light of the particle as your question

	>infers.  It is a Secondary result of the phenomenon associated with
the 
	>speed of the particles in the given medium, with a characteristic 
	>wavelength.  I like the analogy of the sonic boom.... though I'm
not sure I 
	>could explain the phenomenology associated with it.




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