Assertion : ${}^{90}Sr$ from the radioactive fall out from a nuclear bomb ends up in the bones of human beings through the milk consumed by them. It causes impairment of the production of red blood cells.

Reason : The energetic $\beta  – $ particles emitted in the decay of  ${}^{90}Sr$ damage the bone marrow

If half-life of a radioactive atom is $2.3\, days$, then its decay constant would be

If a radioactive material remains $25 \%$ after $16$ days, then its half life will be ……… days

Write a formula showing the relation between half life and average life of a radioactive substance.

Radioactive material $'A'$ has decay constant $8 \lambda$ and material $'B'$ has decay constant $ ' \lambda '$. Initially they have same number of nuclei . After what time, the ratio of number of nuclei of material $'B'$ to that $'A'$ will be $\frac{1}{e}$ ?