Final answer:
Dental X-ray photons are created when electrons are thermally ejected from a hot filament, accelerated, and then collide with a tungsten anode in an X-ray tube, releasing energy as X-ray photons.
Step-by-step explanation:
The photons for dental X-rays originate from an X-ray tube in the dental X-ray machine. This device accelerates electrons from a cathode to an anode made of a heavy metal, such as tungsten, by applying a high voltage. When these electrons collide with the tungsten anode, their kinetic energy is converted to various forms, including x-ray photons.
In more detail, as electrons are ejected by thermal agitation from a hot filament, they travel through a vacuum in the X-ray tube and are accelerated by a high voltage. Upon striking the anode, their kinetic energy generates heat and x-ray photons. These photons emerge when an electron fills a vacancy in an inner shell of a tungsten atom, releasing energy as a photon with a very short wavelength, capable of traversing through soft tissues like gums but mostly absorbed by denser tissues, such as teeth and bones, thus creating an image.