What do you call the amount of radiation deposited per unit length of tissue traversed by incoming photons?

The correct term for the amount of radiation deposited per unit length of tissue traversed by incoming photons is referred to as linear energy transfer (LET). This concept is pivotal in understanding how different types of radiation interact with biological tissues. LET measures the energy transferred by ionizing radiation as it passes through matter. The units typically used for LET are keV/μm, indicating the energy deposited per micrometer of tissue.

Higher LET radiation, such as alpha particles, tends to transfer energy more effectively over a shorter distance compared to lower LET radiation, like gamma rays or X-rays. This distinction is essential in fields such as radiation therapy and radiation protection, as it helps assess the potential biological damage incurred based on the radiation type and energy deposited in tissues.

The other choices focus on broader concepts involving radiation and its effects. Radiation dose typically refers to the total amount of energy absorbed and is not confined to a specific length of tissue. Absorbed dose measures the energy deposited in a given mass of tissue but does not address the idea of tissue thickness in the way LET does. Effective dose takes into account the varying biological effects of different radiations on different tissues, but it does not specify how energy is distributed along a length of tissue.