[en] We considered here the periodic Anderson model and calculate the energy dependent charge susceptibility and dielectric constant which are computed numerically. We observe a low temperature plasmon resonance peak and a hybridization gap at higher energies. We investigate the evolution of the hybridization gap in dielectric constant by varying the position of the f - level , the strength of the hybridization, Coulomb interaction and temperature to explain the MIR experimental observations. We observe two f - electrons in energy dependent charge susceptibility and dielectric constant i.e. a low energy plasmon resonance peak and a gap associated with the strength of the hybridization at higher energies. The low energy resonance peak shifts to still lower energies with increase of the strength of hybridization accompanied by the enhanced strength of the spectral height. The hybridization gap also shifts to lower energies with increase of strength hybridization. These features are observed experimentally in mid infra-red resonance experiments for 1-1-5 family and also in CeIrIn₅. When the position of the f - electron moves from mixed valence state to heavy fermion state the charge susceptibility is suppressed throughout the energy range with prominent hybridization gap. The charge susceptibility is suppressed throughout the energy range with increase of temperature. However, the positions of the resonance peak and the hybridization gap remains unaltered. The dielectric constant is enhanced with Coulomb interaction energy throughout the energy range, indicating the insulating nature of the system. However, the positions of the resonance peak and the hybridization gap remain unaltered. The dielectric constant is suppressed throughout the temperature range with the increase of temperature due to damping effect. However, the suppression of dielectric constant is low at the position of the hybridization gap. The dielectric constant is enhanced throughout the energy range when the position of f - level moves from mixed valence state to the heavy fermion state ( f - electron level moves away from the Fermi level.). (author)