The half-life period of a radioactive element is $140$ days. After $560$ days,one gram of the element will reduce to

The radioactivity of a radioactive element becomes $\frac{1}{10}$ of the original radioactivity after $2.303 \ s$. The half-life period is: (in $s$)

$A$ radioactive element has a half-life of $20 \ \text{minutes}$. How much time should elapse before the element is reduced to $\frac{1}{8}$th of the original mass? (Answer in $\text{minutes}$)

$A$ radioactive isotope decays at such a rate that after $96 \ min$,only $\frac{1}{8}$ of the original amount remains. The half-life of this nuclide in minutes is:

$^{226}Ra$ disintegrates at such a rate that after $3160 \ years$ only one-fourth of its original amount remains. The half-life of $^{226}Ra$ will be .......... $years$.

In a radioactive decay,a uranium atom transforms into a lead atom. If a rock sample from the moon contains an equal number of uranium and lead atoms,and the half-life $(t_{1/2})$ for uranium is $4.5 \times 10^9$ years,then the age of the rock will be: