This study investigates the charge dynamics in graphene using infrared (IR) spectroscopy. Graphene, a single layer of carbon, exhibits unique electronic properties governed by the Dirac Hamiltonian, with massless Dirac quasiparticles and linear energy-momentum dispersion. The research uses IR spectromicroscopy on graphene integrated in gated devices to examine its electronic behavior. The results show that the quasiparticle dynamics in graphene deviate from predictions for ideal, free-standing graphene, indicating the influence of many-body interactions on its electromagnetic response. The study measures the reflectance R(ω) and transmission T(ω) of graphene samples on a SiO₂/Si substrate as a function of gate voltage at 45 K. At the charge neutrality point, the graphene significantly modifies the interference minimum of the substrate, suppressing its reflectance by up to 15%. The reflectance and transmission spectra of graphene structures are modified by gate voltage, showing a dip in R(V)/R(V_CN) spectra at low voltages and a peak-dip structure at higher voltages. The transmission spectra reveal a peak at all voltages, which becomes harder with increasing bias. The frequencies of the main features in R(V)/R(V_CN) and T(V)/T(V_CN) spectra evolve approximately as √V. The 2D optical conductivity of charge-neutral graphene, σ₁(ω, V_CN) + iσ₂(ω, V_CN), is extracted from multilayer analysis. Theoretical analysis predicts a constant "universal" 2D conductivity σ₁(ω, V_CN) = πe²/2h for ideal undoped graphene. The experimental data are consistent with this prediction. The study also reveals that the 2E_F threshold in σ₁(ω, V) shows a width of about 1400 cm⁻¹, independent of gate voltage and carrier density. This width is attributed to disorder effects and electron-phonon coupling. The study finds that the Fermi energy E_F scales with the 2D carrier density N as E_F = ħv_F√(πN). The observed √V dependence of 2E_F substantiates that graphene samples in gated devices are governed by Dirac quasiparticles. The results challenge current theoretical conceptions of fundamental properties of graphene and have implications for its potential applications in optoelectronics. The study also highlights the importance of many-body interactions in determining the electronic properties of graphene.This study investigates the charge dynamics in graphene using infrared (IR) spectroscopy. Graphene, a single layer of carbon, exhibits unique electronic properties governed by the Dirac Hamiltonian, with massless Dirac quasiparticles and linear energy-momentum dispersion. The research uses IR spectromicroscopy on graphene integrated in gated devices to examine its electronic behavior. The results show that the quasiparticle dynamics in graphene deviate from predictions for ideal, free-standing graphene, indicating the influence of many-body interactions on its electromagnetic response. The study measures the reflectance R(ω) and transmission T(ω) of graphene samples on a SiO₂/Si substrate as a function of gate voltage at 45 K. At the charge neutrality point, the graphene significantly modifies the interference minimum of the substrate, suppressing its reflectance by up to 15%. The reflectance and transmission spectra of graphene structures are modified by gate voltage, showing a dip in R(V)/R(V_CN) spectra at low voltages and a peak-dip structure at higher voltages. The transmission spectra reveal a peak at all voltages, which becomes harder with increasing bias. The frequencies of the main features in R(V)/R(V_CN) and T(V)/T(V_CN) spectra evolve approximately as √V. The 2D optical conductivity of charge-neutral graphene, σ₁(ω, V_CN) + iσ₂(ω, V_CN), is extracted from multilayer analysis. Theoretical analysis predicts a constant "universal" 2D conductivity σ₁(ω, V_CN) = πe²/2h for ideal undoped graphene. The experimental data are consistent with this prediction. The study also reveals that the 2E_F threshold in σ₁(ω, V) shows a width of about 1400 cm⁻¹, independent of gate voltage and carrier density. This width is attributed to disorder effects and electron-phonon coupling. The study finds that the Fermi energy E_F scales with the 2D carrier density N as E_F = ħv_F√(πN). The observed √V dependence of 2E_F substantiates that graphene samples in gated devices are governed by Dirac quasiparticles. The results challenge current theoretical conceptions of fundamental properties of graphene and have implications for its potential applications in optoelectronics. The study also highlights the importance of many-body interactions in determining the electronic properties of graphene.