A radioactive material decays by simultaneous emission of two particle...
Since, from Rutherford-Soddy law, the number of atoms left after half-lives is given by
N=N0(1/2)n
where, N0 is the original number of atoms.
The number of half-lives, n= time of decay/effective half−life
Relation between effective disintegration constant (λ) and half-life (T)
λ=ln2/T
∴λ1+λ2= (ln2/ T1)+ (ln2/ T2)
Effective half-life,
1/T=1/T1+1/T2=(1/1620)+(1/810)
1/T=1+2/1620 ⇒T=540yr
∴n=T/540
∴N=N0(1/2)t/540⇒N/N0=(1/2)2=(1/2)t/540
⇒t/540=2⇒t=2×540=1080yr
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A radioactive material decays by simultaneous emission of two particle...
A radioactive material decays by simultaneous emission of two particle...
To solve this problem, we need to understand the concept of radioactive decay and how it relates to half-life.
Half-life is the time it takes for half of a radioactive substance to decay. In this case, we have two particles, each with its own half-life: 1620 years and 810 years.
Let's assume we start with a certain amount of the radioactive material. After 1620 years, half of it will decay, and we will be left with one-half of the original amount. Similarly, after another 1620 years, half of that remaining amount will decay, leaving us with one-fourth of the original amount.
Similarly, for the second particle with a half-life of 810 years, after 810 years, half of the remaining one-fourth will decay, leaving us with one-eighth of the original amount.
Now, we need to find the time at which one-fourth of the material remains, which means we are looking for the time when the amount of material remaining is one-fourth of the original amount.
Let's assume the original amount of the radioactive material is 'x'. After 1620 years, we will have x/2 remaining. After another 1620 years, we will have (x/2)/2 = x/4 remaining.
Similarly, for the second particle, after 810 years, we will have x/8 remaining.
To find the time at which one-fourth of the material remains, we need to equate these two expressions:
x/4 = x/8
Multiplying both sides by 8, we get:
2x = x
Simplifying, we find:
x = 0
This means that the material will decay completely after 0 years. However, this result is not possible because it contradicts the given information that one-fourth of the material remains.
Hence, there must be a mistake in the question or the options provided. The correct answer cannot be determined based on the given information.