(r1) TimeOfPropagation < Cerenkov/Pandacerenkov

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For a transverse path of 1m for Cherenkov light emitted from a particle
of normal incidence in fused silica, 
the time difference for $\beta$=1 and $\beta$=0.99 is only 61ps.
However, due to dispersion both emission angle and speed of light
in the medium are a function of the wavelength.
For 300nm and 600nm photons the time difference is 0.5ns.

$ n_{group} = n_{phase} - \lambda dn_{phase}/d\lambda $

<img src="%ATTACHURLPATH%/panda20a2.gif" alt="fused silica - n_phase and n_group"  width="350" height="270" align=right />
To calculate the propagation speed of the photons
inside the dispersive medium the group velocity has to be used.
The dynamic range of the corresponding group velocity refractive index
is about 3 times larger than that of the normal refractive index.

The figure shows these velocities for fused silica.


-- Main.KlausFoehl - 14 Sep 2005

Topic attachments
I	Attachment	Action	Size	Date	Who	Comment
gif	panda20a2.gif	manage	2.4 K	14 Sep 2005 - 18:07	KlausFoehl	fused silica - n_phase and n_group

Topic revision: r1 - 14 Sep 2005, KlausFoehl

Cerenkov/Pandacerenkov

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