“half-life”的概念、定义、翻译、参考文献-科学参考

half-life

Physics

See decay.

Astronomy

In radioactive decay, the time taken for half the number of atoms initially present to disintegrate. For unstable elementary particles, it is the average time they take to transform spontaneously into other particles, as in for example the beta decay of a free neutron into a proton and electron.

Chemistry

See decay.

Chemical Engineering

The time taken for a substance to fall to half of its original value and is independent of the amount of starting material. A reaction that has a constant half-life is a first-order reaction. Radioactive decay is an example of a first-order reaction. The half-life of a radionuclide is the time for half the nuclei to disintegrate. The time varies between radionuclides ranging from fractions of a second to millions of years. For example, the half-life of beryllium-16 is 2.0×⁻¹⁶ seconds and tellurium-128 is 7.2×10²⁴ years. In biological systems, (p. 175) the half-life is the time taken to naturally excrete half of an absorbed substance from a body or an organ.

Geology and Earth Sciences

See decay constant; radiometric dating.

单词	half-life
释义	half-life Physics See decay. Astronomy In radioactive decay, the time taken for half the number of atoms initially present to disintegrate. For unstable elementary particles, it is the average time they take to transform spontaneously into other particles, as in for example the beta decay of a free neutron into a proton and electron. Chemistry See decay. Chemical Engineering The time taken for a substance to fall to half of its original value and is independent of the amount of starting material. A reaction that has a constant half-life is a first-order reaction. Radioactive decay is an example of a first-order reaction. The half-life of a radionuclide is the time for half the nuclei to disintegrate. The time varies between radionuclides ranging from fractions of a second to millions of years. For example, the half-life of beryllium-16 is 2.0×⁻¹⁶ seconds and tellurium-128 is 7.2×10²⁴ years. In biological systems, (p. 175) the half-life is the time taken to naturally excrete half of an absorbed substance from a body or an organ. Geology and Earth Sciences See decay constant; radiometric dating.
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