nm)
emitted by scintillation or Cherenkov radiation into a longer wavelength (blue light, 
nm) of fluorescent light,
emitted isotropically.
With added wavelength shifters one obtains a considerably increased and well-defined attenuation length in plastic scintillators ( 
Scintillation Counter).
Light from large and/or large-surface scintillator plates can be collected into rods or plates of wavelength shifter material, a technique particularly important in large sampling calorimeters. Wavelength-shifted light also matches better the frequency sensitivity of the receiver (photomultiplier, vacuum diode). On the other hand the decay time of the signal increases to about 10 to 20 ns. In the case of a common light guide for several wavelength shifters each coupled to several scintillators,
only about one sixth of the light is emitted into the cone retained by total reflection.
A good discussion is found in [Aurouet83];
also [Bicron93].