Which statement about alpha radiation is true?

• A. Alpha radiation travels farther in air than gamma rays
• B. Alpha radiation is unaffected by matter
• C. Alpha radiation ionizes less than beta particles
• D. Alpha radiation has higher LET than gamma rays

Answer: (D)

Alpha radiation deposits energy very densely along its short path in matter because alpha particles are heavy and doubly charged. This dense ionization along a compact track is what LET (linear energy transfer) measures—the energy deposited per unit length. Gamma rays are photons that interact less densely with matter and can travel much farther, so their LET is low. That combination makes alpha have a higher LET than gamma rays, so the statement is true.

Why the other ideas don’t fit: alpha travels only a short distance in air, not farther than gamma rays; alpha is not unaffected by matter—it’s quickly absorbed by a small amount of material; and alpha ionizes more, not less, than beta particles due to its greater charge and mass.