Final answer:
At the K-edge, the phosphor absorbs X-rays and subsequently emits characteristic X-rays when an inner-shell vacancy is filled by an electron transition. This helps identify elements due to each element's unique X-ray energy signature.
Step-by-step explanation:
At the K-edge of the phosphor of a receptor, it absorbs X-rays. When the phosphor's atoms de-excite, they emit characteristic X-rays, which are electromagnetic radiation produced after an inner-shell vacancy is filled, often by an electron falling from a higher energy level to an n=1 shell vacancy.
Materials like the phosphor in X-ray detectors are used to capture X-rays and convert the energy into visible light or other forms of lower energy photons, such as the characteristic X-rays mentioned. This helps in the detection and imaging processes. It's also crucial for identifying elements in samples, as each element has its own set of characteristic X-ray energies. The process involves an electron absorption followed by the emission of a photon, which may differ in energy from the absorbed photon, depending on the transitions involved.