Radiations from plasmas are caused by binary collisions between dressed particles which are not point particles. The impulse approximation leads to the result by Dupree. The dressed particle includes naturally the ion correlation as well as the electron correlation, while the screened particle of Birmingham et al. excludes the former. Any cut-off procedures of divergent integrals are made unnecessary by considering both the remote and close collisions. In certain cases the radiation is enhanced by collective interactions. An example is given in which the spectrum is expressed in terms of elementary functions.