Study of the Nuclear Transparency Effect at 4.2 A GeV/c The use of nuclear transparency effect of protons, p + - and p - - mesons in proton, and deuteron induced interactions with carbon at 4.2 A GeV/c, to get information about properties of nuclear matter is reported in this work. Half angle (θ 1/2 ) technique is used to extract the nuclear transparency effect. The θ 1/2 divides the multiplicity of charged particles produced in nucleon-nucleon collisions into two equal parts depending on their polar angle in the lab. frame. Particles with angle smaller than (incone particles) and greater than (outcone particles) θ 1/2 are considered separate. The average values of multiplicity, momentum and transverse momentum of the protons p + - and p - - mesons are analyzed as a function of a number of identified protons in an event. We observed evidences in the data which could be considered as transparency effect. For quantitative analysis, the results are compared with cascade model. The observed effects are categorized into leading effect transparency and medium effect transparency. Analysis of the results shows that the leading effect is the basis of the observed transparency in the former case. The transparency in the latter case could be the reason of collective interactions of grouped nucleons with the incident particles.