What percentage of attenuation is provided by a 0.5-mm apron for a 50-kVp beam?

A 0.5-mm lead apron provides significant attenuation of radiation, especially at lower energies, such as a 50-kVp beam. At this level of radiation energy, the effectiveness of lead in attenuating the beam is quite high. Empirical data and studies in radiation protection have shown that a 0.5-mm lead apron can attenuate approximately 99% of the radiation at the specified energy.

This remarkable level of attenuation is crucial in personnel protection, as it helps to reduce the exposure to ionizing radiation for individuals working in environments where they are at risk, such as medical imaging or radiation therapy.

For context, lower or higher thicknesses of lead would result in varying percentages of attenuation. In this case, the value of 99% indicates that the 0.5-mm apron provides almost complete protection against the radiation indicated, which is why this answer stands out as the correct choice.