Which is the correct expression for half-life
${(t)_{1/2}} = \log \,2$
${(t)_{1/2}} = \frac{\lambda }{{\log \,2}}$
${(t)_{1/2}} = \frac{\lambda }{{\log \,{\rm{2}}}}(\,2.303)$
${(t)_{1/2}} = \frac{{2.303\,{\rm{ log\,2}}}}{\lambda }$
Give a brief explanation about radioactivity.
A radioactive nucleus decays by two different process. The half life of the first process is $5$ minutes and that of the second process is $30\,s$. The effective half-life of the nucleus is calculated to be $\frac{\alpha}{11}\,s$. The value of $\alpha$ is $..............$
Write down the definition and formula of half life of radioactive substance.
Which of the following statements are true regarding radioactivity
$(I)$ All radioactive elements decay exponentially with time
$(II)$ Half life time of a radioactive element is time required for one half of the radioactive atoms to disintegrate
$(III)$ Age of earth can be determined with the help of radioactive dating
$(IV)$ Half life time of a radioactive element is $50\%$ of its average life periodSelect correct answer using the codes given belowCodes :
Two radioactive substances $X$ and $Y$ originally have $N _{1}$ and $N _{2}$ nuclei respectively. Half life of $X$ is half of the half life of $Y$. After three half lives of $Y$, number of nuclei of both are equal. The ratio $\frac{ N _{1}}{ N _{2}}$ will be equal to