1.

A radioactive element X with a half life of 2 hours decays giving a satble element Y. After a time t, the ratio of X to Y atoms is 1 : 7, then time t is :

Answer»

6 hours
4 hours
between 4 to 6 hours
14 hours

Solution :After two HOUR, X=1, y=7
x+y=1+7=8
so, if x =N=1
then x+y `=N_(0)=8`
`N/N_(0)=(1/2)^(n)`
or `1/8=(1/2)^(n) or (1/2)^(3)=(1/2)^n`
n=3 half LIFE PERIOD `=3 xx 2=6"hours"`.


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