Question

The half life of Radium is 1600 years after how many years 25% of Radium block remains undecayed

Answer 1

Answer:

8000 years

Explanation:the half life of radium is known to be 16000 then 25% means half of 50%

Which means 16000/2= 8000

So for about 8000 years the radium block remains undecayed

Answer 2

25% of Radium block remains undecayed after 3200 years

Explanation:

Let initial amount of radium=$N_0$

Half life of radium=1600 years

The quantity left after n half lives=N=25% of $N_0$=$\frac{1}{4}N_0$

The amount of radioactive element after n half lives is given by

$N=N_0(\frac{1}{2})^n$

Where n=Number of half lives

$N_0$=Initial amount of radioactive element

N=Amount left of radioactive element after n half lives

Substitute the values then we get

$\frac{N_0}{4}=N_0(\frac{1}{2})^n$

$(\frac{1}{2})^2=(\frac{1}{2})^n$

When base are equal on both sides of equal to then power will be equal therefore,

$n=2$

Time of disintegration=$Number\;of\;half\;,lives\times half\;life$

Time of disintegration=$1600\times 2=3200$ years

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https://brainly.in/question/3243577:Answered by Danielochich