What type of photons can penetrate many materials, including human tissue?

Gamma photons are a form of electromagnetic radiation that have high energy and can penetrate various materials, including human tissue. Their penetrating ability is due to their short wavelength and high frequency, which allows them to pass through substances that can block less energetic forms of radiation, such as alpha and beta particles.

Alpha particles, on the other hand, are composed of helium nuclei and have a low penetration power; they can be stopped by just a sheet of paper or the outer layer of human skin. Beta particles, which are high-energy, high-speed electrons or positrons, have greater penetrating power than alpha particles but are still limited when it comes to penetrating dense materials or human tissue.

X-rays, like gamma rays, are also a form of high-energy electromagnetic radiation, but they are generally less penetrating than gamma photons under similar conditions. Thus, while both gamma photons and X-rays can penetrate materials, gamma photons are typically more capable due to their higher energy levels.

Overall, gamma photons are distinguished by their ability to penetrate deeper and more effectively than the other forms of radiation mentioned, making them the correct answer in this context.