What is the SI unit of kerma?

The correct choice for the SI unit of kerma is joules per kilogram (J/kg). Kerma, which stands for kinetic energy released per unit mass, is a measure used in radiation therapy and dosimetry to quantify the energy transferred from radiation to matter, specifically in a given mass of material. This quantity is crucial in assessing how much energy from ionizing radiation can cause biological effects, making it significant in medical physics and dosimetry.

The unit J/kg effectively conveys the relationship between energy and mass, aligning with the principles of energy deposition in radiological contexts. By defining kerma in this manner, it emphasizes that kerma represents the kinetic energy imparted to charged particles by uncharged ionizing radiation, divided by the mass of the material affected.

Other options do not represent kerma correctly:

• Gray (Gy) is a unit of absorbed dose, reflecting the amount of radiation energy absorbed by a tissue per kilogram but does not specifically measure the kinetic energy released.

• Joules per square meter (J/m²) is a unit of energy density but is not applicable to the context of kerma, as it does not take mass into account.

• The roentgen (R) is a unit that quantifies exposure to