Interaction between electromagnetic waves and dense or over dense plasma has recently been noticed in many aspects. Damping of these waves could transfer energy. Radio waves with appropriate wavelength stimulate electrons in upper hybrid resonance and produce waves which are effective for heating of dense plasma in spherical tokamaks. Laser waves with wavelengths the range few hundreds anometer have been used in over dense plasmas. Phenomenon like scattering off of electron acoustic waves (EAW) with frequencies below the plasma frequency (? ? p) which reflect incident waves produce instabilities in plasma that play important role for success of fusion. A two-dimensional (2D), Vlasov-Maxwell code was used to investigate the time evolution of the electron distribution function in dense plasma (Mega Amper Spherical tokamak) and over dense plasma (plasma at Inertial Confinement Fusion). We could calculate k? D quantity by determining Debye length and using different wavelengths. It was found that because there were some instabilities as a result of stimulated electron scattering, this wave was observed at a frequency and phase velocity (? 0.54? p , v ? 1.93v t,e ) below that of the plasma frequency. They could
