x-rays are made by hitting metal with fast-moving electrons. they are photons, tiny packets of energy that can move atoms and change chemicals in the body. they are ionizing radiation but the things they do depend on the wavelength of the x-rays (or how much energy they have). x-rays with smaller energies ("soft" x-rays) cause the photoelectric effect. mid-level energies cause compton scattering. high-level energies ("hard" x-rays) cause pair production. x-rays used for making pictures of people have low to medium energy. radiation therapy that treats cancer uses compton scattering and sometimes pair production.