Number of Cherenkov photons produced by electrons, protons, helium ions and muons that pass through a 40 mm thick block of aerogel as function of their kinetic energy E _kin. The calculations were made for the wavelength interval from λ ₁ = 300 nm to λ ₂ = 500 nm under the assumption of a constant refractive index n = 1.05 by integrating the Frank-Tamm formula (Eq. 2) over the given wavelength interval.