Which type of radiation has the greatest penetrating power?

Gamma rays possess the greatest penetrating power of all the types of radiation listed. This is primarily due to their nature: gamma rays are high-energy electromagnetic waves with no mass and no charge, allowing them to easily pass through various forms of matter, including human tissue and dense materials like lead or concrete.

In contrast, alpha particles are relatively heavy and positively charged, which makes them easily absorbed by even a sheet of paper or the outer layer of human skin. Beta particles, which are electrons or positrons, have more penetrating ability than alpha particles, but they still can be stopped by materials like plastic or aluminum. X-rays, while also having significant penetrating power, generally do not penetrate as deeply as gamma rays due to their lower energy levels.

Thus, gamma rays' high energy and lack of charge and mass contribute to their ability to penetrate substantial barriers, solidifying their status as the form of radiation with the greatest penetrating power.