Question

25. If the half life of a material is 10 years, then in what
time, it becomes th part of the initial amount?
(1) 15 years
(2) 20 years
(3) 25 years
4 30 years
​

Answer 1

$\huge\underline{\underline{\bf \orange{Correct\:Question-}}}$

the half life of a material is 10 years, then in what

time, it becomes ¼th part of the initial amount?

$\huge\underline{\underline{\bf \orange{Solution-}}}$

$\large\underline{\underline{\sf Given:}}$

• Half life = 10 years
• ${\sf \dfrac{N}{N_o}=\dfrac{1}{4}}$

$\large\underline{\underline{\sf To\:Find:}}$

• Time (T)

✪$\large{\boxed{\bf \blue{\dfrac{N}{N_o}=\left(\dfrac{1}{2}\right)^n} }}$

$\implies{\sf \dfrac{1}{4}=\left(\dfrac{1}{2}\right)^2 }$

$\implies{\sf \left(\dfrac{1}{2}\right)^2=\left(\dfrac{1}{2}\right)^n }$

$\implies{\sf n = 2}$

Now ,

✪$\large{\boxed{\bf \blue{ T = n×t^{1/2}}}}$

$\implies{\sf T = 2×10}$

$\implies{\bf \red{Time\:(T)=20\:years}}$

$\huge\underline{\underline{\bf \orange{Answer-}}}$

Option (2) 20 years

Answer 2

Answer:

Option 2 is the answer

20 Years ________