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A radioactive substance decays at a rate proportional to the amount of substance present. If half of the substance decays in 100 years, then what is the decay constant (proportionality constant) ?

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Concept

Half-life:  

Where k is the decay constant.

Calculation:

We know that  

Putting the value of t1/2 = 100 years,

⇒ 100 = 

⇒ k = 

∴ Decay constant is .

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