What primary factor is considered for the effectiveness of radiation shielding?

The primary factor that determines the effectiveness of radiation shielding is the density and atomic number of the shielding material. Materials with higher atomic numbers and greater density are more effective at attenuating radiation. This is because dense materials have more mass per unit volume, which helps to absorb and scatter the high-energy photons associated with radiation.

Higher atomic number elements have more electrons, which can also interact effectively with gamma rays and X-rays, leading to increased attenuation. For instance, materials like lead (high density and high atomic number) are commonly used in radiation shielding due to their superior ability to reduce radiation exposure compared to materials with lower density or atomic numbers.

Other factors, such as the cost of materials and the size of the shielding equipment, may be important in practical applications, but they do not fundamentally affect the shielding effectiveness in the same way that the material's density and atomic number do. The color of the shielding material is irrelevant to its ability to protect against radiation, as it does not influence the interaction between radiation and the material itself.