A mixture consists of two radioactive materials A_1 and A_2 with half lives of 20 ~s and 10 ~s respectively. Initially the mixture has 40 ~g of A_1 and 160 ~g of A_2 . The amount of the two in the mixture will become

Correct answer: D. 40 ~s For 40 ~g amount 40 ~g half -life 20 ~s 20 ~g 20 ~s 10 ~g For 160 ~g amount array l 160 ~g 10 ~s 80 ~g 10 ~s 40 ~g 40 ~g 10 ~s 20 ~g 10 ~s 10 ~g array So, after 40 ~s A_1 and A_2 remains same.

NEET 2012

Exam: NEET
Year: 2012
Subject: Physics
Chapter: Nuclear Physics

NEET 2012 · Physics · Nuclear Physics

A mixture consists of two radioactive materials A_1 and A_2 with...

A mixture consists of two radioactive materials

A_1

and

A_2

with half lives of

20 \mathrm{~s}

and

10 \mathrm{~s}

respectively. Initially the mixture has

40 \mathrm{~g}

A_1

and

160 \mathrm{~g}

A_2

. The amount of the two in the mixture will become equal after

Options

A $60 \mathrm{~s}$
B $80 \mathrm{~s}$
C $20 \mathrm{~s}$
D $40 \mathrm{~s}$

Correct answer

D. $40 \mathrm{~s}$

Step-by-step solution

For

40 \mathrm{~g}

amount

40 \mathrm{~g} \underset{\text{ half -life }}{\stackrel{20 \mathrm{~s}}{\longrightarrow}} 20 \mathrm{~g} \stackrel{20 \mathrm{~s}}{\longrightarrow} 10 \mathrm{~g}

For

160 \mathrm{~g}

amount

\begin{array}{l} 160 \mathrm{~g} \stackrel{10 \mathrm{~s}}{\longrightarrow} 80 \mathrm{~g} \stackrel{10 \mathrm{~s}}{\longrightarrow} 40 \mathrm{~g} \\ 40 \mathrm{~g} \stackrel{10 \mathrm{~s}}{\longrightarrow} 20 \mathrm{~g} \stackrel{10 \mathrm{~s}}{\longrightarrow} 10 \mathrm{~g} \end{array}

So, after

40 \mathrm{~s} A_1

and A_2 remains same.

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