Which radiation property is associated with greater biological harm per unit absorbed dose?

• A. Energy
• B. Frequency
• C. Velocity
• D. LET

Answer: (D)

Biological damage at a given absorbed dose depends on how energy is deposited in tissue, not only on the total energy absorbed. Linear energy transfer describes how much energy is deposited per unit length as the radiation travels. When LET is high, energy is dumped densely along the track, causing complex, clustered DNA damage that’s harder for cells to repair, so the same absorbed dose results in greater harm. Low-LET radiation spreads energy more sparsely, producing mostly simpler damage that cells can repair more easily, so its harm per unit dose is less. Energy alone measures how much energy is absorbed, frequency relates to photon energy but not how that energy is distributed, and velocity doesn’t reflect the pattern of energy deposition. So the property that best predicts greater harm per unit absorbed dose is linear energy transfer.