Final answer:
X-ray photons produced from outside the focal spot of a CRT device entail high-energy electrons being accelerated and striking an anode, leading to the emission of high-frequency electromagnetic radiation that requires lead or concrete shielding due to their penetration ability.
Step-by-step explanation:
X-rays are produced by bombarding a metal target with high-energy electrons. These electrons are accelerated through a high voltage, obtaining kinetic energy, which is converted into various forms including x-ray photons upon striking an anode. The process can be observed in a device known as a cathode ray tube (CRT), where electrons ejected from a hot filament by thermal agitation are accelerated. A key characteristic of x-rays is their ability to travel long distances in air, up to half a kilometer, and their penetration ability, which means they require a thick layer of lead or concrete shielding to be stopped. When discussing x-ray production, it is important to note that x-rays are high-frequency electromagnetic radiation, produced by transitions between inner-shell electron levels or by the deceleration of electrons, yielding x-rays characteristic of the atomic element.