A charged particle of mass m and having a charge Q is placed in an electric field E which varies with time as E=E0sinωt. What is the amplitude of the S.H.M. executed by the particle?

For a particle undergoing SHM with an amplitude A and  angular frequency ω, the maximum acceleration =ω2 A Here the maximum force on the particle =QE0∴ maximum acceleration =QE0 m=ω2 A⇒A=QE0 mω2