Which of the following ionizing radiations has the highest LET?

Which of the following ionizing radiations has the highest LET?

• A. Beta
• B. Gamma
• C. Alpha
• D. X-rays

Answer: (C)

The concept of Linear Energy Transfer (LET) describes the amount of energy that ionizing radiation transfers to the medium it passes through, typically expressed in keV/µm. The type of radiation that has the highest LET is alpha particles.

Alpha particles are heavy, positively charged particles composed of two protons and two neutrons. Due to their mass and charge, alpha particles interact with matter more intensely than lighter particles, such as beta particles or electromagnetic radiation like gamma rays and x-rays. This higher mass and charge lead to more frequent ionization events along their path, thereby resulting in a higher concentration of energy deposited into the medium.

In contrast, beta particles—which are electrons or positrons—have lower mass and charge, leading them to interact less intensely with matter compared to alpha particles. Gamma rays and x-rays, which are forms of electromagnetic radiation, have negligible mass and charge, resulting in even lower LET because they travel longer distances without significantly interacting with matter before being absorbed.

Therefore, the characteristic properties of alpha particles contribute to their classification as having the highest LET among the types of ionizing radiation listed.