What are the effects of radiation on living tissue?
Radiation travels in a wavelike manner. It depends on its intensity. The higher the intensity of the radiation, the shorter its wavelength and the higher the energy it has or imparts.
Radiowaves for example has a weak intensity and doesn't really do much damage. Sunlight has a visible and ultraviolet radiation. The ultraviolet radiation causes oxidative damage to your skin making you age faster. gotta stay away from that.
X-ray and Gamma rays are radiation of a much higher intensity. You might imagine this as "invisible microscopic knives" cutting thru your body and exiting on a constant rate without "leaving a mark". But the effects are real though. Radiation can break and alter your molecular bonds and your DNA. These "invisible knives" may mutate or break these molecules.