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Forum: Processes Involving Optical Photons
Re: Sad Cerenkov Spectral Shape (Nicole Ackerman)
Re: Question Re: Cerenkov Spectral Shape (Eric)
Date: 19 Oct, 2011
From: Nicole Ackerman <Nicole Ackerman>

Hi Eric,

The "problem" is whether we are thinking about number of photons per energy (or frequency) or wavelength. In energy the spectrum is flat, but in wavelength space it is not. When we think of the "color" of light we are typically thinking in wavelength space. There is a nice summary on page 22 of the 1958 Cerenkov textbook by Jelley:

Number of photons per unit path per unit frequency interval is constant

Number of photons per unit path per unit wavelength interval is proportional to 1/lambda^2.

For optical photons in water, the path length is unrelated to wavelength. It would be important to consider them together if there was a significant change in n over the optical wavelength.

So there is no problem with Geant4, it is simply how we choose to plot the data.


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1 Note: Re: Cerenkov Spectral Shape   (Yusuf - 25 Oct, 2011)
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