Energy and Absorption
The energy of the alpha emitted in alpha decay is mildly dependent on the half-life for the emission process, with many orders of magnitude differences in half-life being associated with energy changes of less than 50% (see alpha decay). The energy of alpha particles emitted varies, with higher energy alpha particles being emitted from larger nuclei, but most alpha particles have energies of between 3 and 7 MeV (mega-electron-volts), corresponding to extremely long to extremely short half-lives of alpha-emitting nuclides, respectively.
This energy is a substantial amount of energy for a single particle, but their high mass means alpha particles have a lower speed (with a typical kinetic energy of 5 MeV; the speed is 15,000 km/s, which is 5% of the speed of light) than any other common type of radiation (β particles, neutrons, etc.) Because of their charge and large mass, alpha particles are easily absorbed by materials, and they can travel only a few centimetres in air. They can be absorbed by tissue paper or the outer layers of human skin (about 40 micrometres, equivalent to a few cells deep).
Read more about this topic: Alpha Particle
Famous quotes containing the words energy and/or absorption:
“The very presence of guilt, let alone its tenacity, implies imbalance: Something, we suspect, is getting more of our energy than warrants, at the expense of something else, we suspect, that deserves more of our energy than we’re giving.”
—Melinda M. Marshall (20th century)
“The radio ... goes on early in the morning and is listened to at all hours of the day, until nine, ten and often eleven o’clock in the evening. This is certainly a sign that the grown-ups have infinite patience, but it also means that the power of absorption of their brains is pretty limited, with exceptions, of course—I don’t want to hurt anyone’s feelings. One or two news bulletins would be ample per day! But the old geese, well—I’ve said my piece!”
—Anne Frank (1929–1945)