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Flavia
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Radioactive sample activity is said decreases by factor 5 during 2-h interval. How to find the decay constant? If the given initial value is not given? I don't know how to calculate.
tiny-tim said:Hi Flavia! Welcome to PF!
Call the initial value "A", and write out an equation to show when it reaches A/5 …
what do you get?
tiny-tim said:divide both sides by A !
Flavia said:If it given initial activity 10 mci, how to know the number of atom inside?
tiny-tim said:you mean mCi ?
see http://en.wikipedia.org/wiki/Curie …
The curie (symbol Ci) is a non-SI unit of radioactivity, named after Marie and Pierre Curie. It is defined as
1 Ci = 3.7 × 1010 decays per second.Its continued use is discouraged.
…
Curies are occasionally used to express a quantity of radioactive material rather than a decay rate, such as when one refers to 1 Ci of cesium-137.
This may be interpreted as the number of atoms that would produce 1 Ci of radiation. The rules of radioactive decay may be used convert this to an actual number of atoms. They state that 1 Ci of radioactive atoms would follow the expression:
N (atoms) * λ (1/s) = 1 Ci = 3.7 × 1010 (Bq)and so,
N = 3.7 × 1010 / λwhere λ is the decay constant in s-1.
Flavia said:2)What is seven half life mean? Is it 7T1/2 = value?
1)If given half life. how to get initial decay rate?
From half life, i can get the λ.
Ro = λNo. how to get No?
Flavia said:1)If given half life. how to get initial decay rate?
-the question is, the half life of Ga-67 is 78 hours. Calculate initial decay rate
To calculate decay constant without knowing the initial value, you can use the half-life formula: t1/2 = ln(2)/λ, where t1/2 is the half-life and λ is the decay constant. Rearrange the formula to solve for λ, and then use the decay constant to calculate the remaining values.
No, decay constant cannot be negative. It is a positive value that represents the rate at which a substance decays. A negative decay constant would imply that the substance is increasing in quantity over time, which goes against the principles of decay.
Decay constant is typically measured in units of inverse time, such as inverse seconds (s-1) or inverse years (yr-1). This is because it represents the rate of decay over a specific time period.
The initial value does not affect the decay constant. The decay constant is a characteristic property of a substance, and it remains constant regardless of the initial value. However, the initial value can affect the half-life and the amount of substance remaining at a given time.
Yes, decay constant can be used to predict the amount of substance remaining at a specific time. By rearranging the half-life formula to solve for the remaining amount of substance at a given time, you can use the decay constant to calculate the predicted value. However, this prediction is based on the assumption that the decay rate remains constant over time.