Radio waves can be produced by oscillations in electrical circuits (Higher tier). When radio waves are absorbed by a receiver, they create an alternating current in its circuit with the same frequency as the radio wave. So radio waves can themselves induce oscillations in an electrical circuit.
Changes in atoms and in the nuclei of atoms can generate or absorb electromagnetic waves over a wide range of frequencies. Gamma rays originate from changes in the nucleus of an atom.
Ultraviolet waves, X-rays and gamma rays can have hazardous effects on human body tissue. The effect depends on the type of radiation and the size of the dose. Radiation dose is measured in sieverts (Sv) and tells you the risk of harm from an exposure. 1000 millisieverts (mSv) = 1 sievert, so a dose of 3 sieverts is 3000 millisieverts. Ultraviolet can make skin age early and increases the risk of skin cancer. X-rays and gamma rays are ionising radiation. They can cause genes to mutate, and this can cause cancer.