Question

Q.a radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains is.
a). 1080 b). 2430
b). 3240 d). 4860
explain with clear explanation. {class 12th Q.}

[last 6 year continous asked question in board exam of 5mark.] ​

Answer 1

since,from Rutherford _soddy low,

the number of atoms left half lives is given by,

N=Nnot (1/2)^n

where,No is the original number of atims

The number of half lives in=time of decay/egfective half-cycle

relation between effective distegration constant (lemda)&half life(T)

lemda=In2/T

lemda1+lemda2=In2/T1+In2/T2

effective half life,

1/T=1/T1+1/T2

=1/1620+1/810

1/T=1+2/1620

T=540 year

n=T/540

N=N not (1/2)^t/540

N/N not=(1/2)^2

=(1/2)^t/540

t/540=2

t=2×540=1080year

hope it helps u topper

Answer 2

Answer:

Sorry I don't know the answer