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We study the propagation of Cerenkov photons generated by Very High Energygamma-rays and hadrons in the atmosphere. The photon production heightdistributions are estimated from semi-empirical methods and compared with thosederived by standard simulation techniques. Incident spectra at variousobservation altitudes are then derived after applying wavelength dependentcorrections due to photon attenuation in the atmosphere during the propagationof photons from the height of production to the height of observation. Theseare generated both for gamma- and hadron primaries of various energies. Thederived production height distributions agree very well with those generated bythe simulation package `CORSIKA' at all energies and for both gamma-$ray andproton primaries. The incident photon spectra are found to be both altitudedependent and primary energy dependent. The peak of the incident spectrumshifts towards the shorter wavelength with increasing altitude of observationfor a given primary. Also the peak of the photon spectrum shifts towards theshorter wavelength with increasing energy of the primary at given altitude. Thefraction of the UV component in the incident Cerenkov spectrum is estimatedboth for gamma-ray and hadronic primaries at various observation altitudes andenergies. Hadron generated Cerenkov spectra are marginally richer in UV lightand the difference increases slightly at higher altitudes. The fraction of theUV to the visible light in the Cerenkov spectrum could be a useful parameter toseparate gamma-rays from cosmic ray background only if one can measure thisfraction very accurately.Comment: 22 pages, Latex with 8 postscript figures; to appear in Experimental  Astronom

Gamma Ray and Hadron generated Čerenkov Photon Spectra at Various Observation Altitudes