The radiation that can penetrate deepest in our body :

The ability of radioactivity to pass through materials is called its penetrating ability. Penetrating ability depends on the size of the radioactive particle. Alpha particles are the biggest, beta particles are very much smaller and gamma rays have no mass. Ultraviolet rays have less energetic photons compared to gamma rays to gamma rays and x-rays and a lower penetration power. Gamma rays are the most penetrating of the radiations