If the half-life of a certain radioactive nucleus is $1000 \ s,$ the disintegration constant is

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:

If a substance with a half-life of $3 \ days$ is kept for $12 \ days$,what fraction of the substance remains?

The half-life of a radioactive disintegration $(A \to B)$ having a rate constant of $231 \ sec^{-1}$ is:

The rate constant for a radioactive decay reaction is $\lambda$. The average life is represented by:

The half-life of the radio element $_{83}Bi^{210}$ is $5 \ days$. Starting with $20 \ g$ of this isotope,the amount remaining after $15 \ days$ is ......... $g$. (in $g$)