Final answer:
A CR reader uses intense light to release the trapped electrons in an imaging plate through a process similar to the photoelectric effect.
Step-by-step explanation:
A Computed Radiography (CR) reader uses light to release 'trapped' electrons in the imaging plate. The process by which this happens is akin to the photoelectric effect, where light causes electrons to be ejected from a material. In the case of the CR reader, the imaging plate is coated with photostimulable phosphors, such as barium fluorohalide. When these phosphors are exposed to x-rays during imaging, they store energy by 'trapping' electrons in a higher energy state. Then, in the CR reader, the plate is exposed to intense light (usually from a laser), which provides the energy to release these trapped electrons, causing them to return to their ground state. As they relax back to lower energy levels, they emit light, which is detected and used to create the digital image.