Interactive comparison: Quantity control & Penetrating power
mA controls the electrical current through the X-ray tube. More mA means more electrons travel from the cathode to the anode. More electrons striking the anode means more X-ray photons are produced.
Activity/source strength controls the quantity of gamma radiation emitted. Higher activity means more gamma rays are emitted from the source.
kV controls X-ray penetrating power. Increasing kV gives X-ray photons more energy, allowing them to penetrate thicker or denser materials. X-ray penetrating power can be changed at the press of a button.
To change gamma ray penetrating power, you must change the isotope. Ir-192 is less penetrating; Co-60 is more penetrating. There is no button to press to change the penetrating power.