Alpha particles travel approximately how far in air?

Alpha particles travel approximately how far in air?

• A. Several millimeters.
• B. Several centimeters.
• C. Several meters.
• D. Several kilometers.

Answer: (B)

Alpha particles are heavy, positively charged helium nuclei that lose energy very quickly as they collide with air molecules. This strong interaction gives them a high stopping power, so they deposit energy over a short distance and come to rest after only a few centimeters in air under normal conditions. For typical alpha energies around a few MeV, the practical range in air is on the order of several centimeters—enough that a sheet of paper can stop many of them. If the energy were much higher, the range would increase, but it would still not reach meters or kilometers in ordinary air. So the short, a few-centimeter travel distance in air reflects their high rate of energy loss and limited penetration.

Alpha particles are heavy, positively charged helium nuclei that lose energy very quickly as they collide with air molecules. This strong interaction gives them a high stopping power, so they deposit energy over a short distance and come to rest after only a few centimeters in air under normal conditions. For typical alpha energies around a few MeV, the practical range in air is on the order of several centimeters—enough that a sheet of paper can stop many of them. If the energy were much higher, the range would increase, but it would still not reach meters or kilometers in ordinary air. So the short, a few-centimeter travel distance in air reflects their high rate of energy loss and limited penetration.