Which two of the following measurements are commonly used to describe the quantity of radiation in the x-ray beam?

Air kerma and exposure are commonly used to quantify radiation in the x-ray beam, making them integral to understanding radiographic dose measurement.

Air kerma, measured in gray (Gy), specifically describes the kinetic energy transferred from photons to electrons in air, making it a direct measure of radiation energy delivered to a specific area. It's particularly important in radiation protection and dosimetry, as it provides an understanding of the radiation's potency in terms of energy transfer.

Exposure, calibrated in roentgens (R), quantifies the amount of ionization produced in air by x-ray or gamma radiation. It measures how much radiation is present in the air, serving essential roles in diagnostic and therapeutic radiology. Understanding exposure is crucial for ensuring patient safety and optimizing imaging protocols.

In contrast, effective dose and entrance dose, while related to radiation exposure and impacts on patients, do not directly measure the radiation quantity present in the x-ray beam itself and are thus not as suitable for this particular question about radiation quantity descriptors. Effective dose considers the biological effects of radiation on various tissues, while entrance dose focuses on the radiation dose that enters the patient’s body, leading to different applications in radiation safety and risk assessment rather than direct measurement of beam quantity.