Answer:
A half-life is the amount of time needed for half of an atomic nuclide in a given sample to react, or the amount of time needed for neutrons to decay into proton, electron, and antineutrino groups. This is a mechanism that occurs in many different kinds of nuclear and chemical incidents, such as the decay of radioactive isotopes or nuclei.
The Detection of Half-Lives
Ernest Rutherford, one of the leading scientists of his day, is credited with discovering half-lives as well as alpha and beta radiation. Alongside scientist Joseph John Thompson, Rutherford conducted complementary experiments that ultimately led to the discovery of electrons, placing him at the forefront of this momentous discovery. Research on radioactivity started when Rutherford realized the possibilities of what he was seeing. The difference between beta and alpha radiation was discovered by him two years later. Since samples of radioactive materials decayed by half in the same period, this led to his discovery of half-lives.
Derivation of the Half Life Formula
We first begin with the exponential decay law, which is expressed as follows:
N(t) = N0e −λt
Additionally, one needs to set t = T1/2 and N (T1/2) = ½ N0
N (T1/2) = 1/2N0 = N0e – λT1/2
Next, calculate the logarithm by dividing by N0.
½ = e −λt
Thus, In (1/2) = −λT1/2
Now solving for T1/2,
T1/2 = −1λ In (1/2)
The “-1” can be raised to an exponent of the logarithm using the logarithmic rules. Ultimately, this provides
T1/2 = In (2))/λ
The Half-Life of Certain Substances
Here are some examples of elements and their associated half-lives, as the half-life formula has been used to determine the half-lives of several isotopes:
Silver-94 – 0.42 seconds
Neutron – 10.2 min
Iodine-131 – 8 days
Carbon-14 – 5,730 years
Plutonium-239 – 24,100 years
A Few Examples of the Half-Life Formula
Question: If we were to calculate a certain radioactive substance’s half-life and use a decay constant of 0.003 per year, the result would be ____.
Solution: t1/2 = ln (2)/λ
t1/2 = 0.693 / 0.003 yearly
t1/2 = 231 years
In other words, this indicates that the half-life of the material in question is 231 years and that half of it will take that long to decompose.
Question: Determine the decay constant value of a radioactive material with a half-life of 0.04 seconds.
Solution: Given that the substance’s half-life is t1/2 = 0.04
To determine a substance’s half-life, apply the half-life formula.
t1/2 = 0.693/λ
λ= 0.693/0.04
= 17.325
Thus, 17.325 s-1 is the radioactive substance’s decay constant.
Question: If the material contains 90% of the carbon-14 present in living tissue, then calculate the age of the Shroud of Turin.
Solution: The original equation’s N(t)/N0 equals 90%, or 0.90, which can be changed to 0.90= e(λ*t).
Since the value of lambda is unknown, we can utilize the first half-life formula, which yields 0.693 over 5730 years since the half-life of carbon-14 is known.
Returning to the previous equation, we can see that ln 0.90 = -λt by calculating the natural logarithm of both sides.
We would get t = ln 0.90/λ by rearranging this new equation to isolate t.
Solving the two equations for time t and changing lambda to the appropriate equation
t = ln 0.90/ (0.693/5730 years)
t = 871 years
What Are the Applications of Half-Life?
Geologists and archaeologists and even physicians use this formula. Some of the notable applications of half-life are:
- The formula has been used in the medical industry, where injections of radioactive materials into patients are most likely to occur to establish the safe handling duration. According to an established protocol, a sample is considered safe once its radioactivity falls below detection limits, which happens every ten half-lives.
- Experts utilize the process of radioactive dating to ascertain the age of a variety of artifacts and other materials, including rocks and ancient things. The precise ages of rocks, other geological features, and man-made things on Earth are among the details it provides regarding their attributions.
- For organic entities to function, carbon is necessary. While both carbon-12 and carbon-13 are stable isotopes, carbon-12 is the most prevalent and may be found in almost all organic structures. Carbon-14, an unstable isotope generated in the atmosphere by radiation from space which is also found on Earth.
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