A physics resident logs four observations: a Tc-99m nucleus passes its excitation energy to an inner orbital electron, an inner-shell vacancy is followed by low-energy electron emission, beta particles stopped in thick lead create a broad x-ray continuum, and a gamma beam weakens exponentially as absorber thickness grows. Which radiation physics phenomenon accounts for each observation in order?

Internal conversion is a decay event: the excited nucleus transfers energy directly to an inner orbital electron and ejects it, so the electron leaves with a discrete energy instead of a gamma ray. Auger emission happens when the vacancy left in an inner shell is filled and part of the released energy kicks out a low-energy electron with very short range and heavy local deposition. Bremsstrahlung is a shielding issue, because a beta particle decelerating in the field of a high-atomic-number nucleus radiates a continuous spread of photon energies. Attenuation is a beam property, describing exponential removal of photons through an absorber by photoelectric absorption, Compton scattering, coherent scattering, and pair production. Lead characteristic x-rays fail the continuum requirement because fluorescence leaves at discrete line energies. Photoelectric absorption fails the decay-mechanism requirement, since it is an interaction between a photon and atomic electrons instead of a nuclear transition. The inverse-square law fails the absorber requirement, because it describes geometric spread with distance, unchanged by added absorber. Exam caveat: beta shielding is often tested as low-atomic-number backing first, with lead behind it to catch the bremsstrahlung. Practical check: if a survey reading jumps after lead is added around a beta source, suspect bremsstrahlung before a detector fault.