Questions in nuclei

Select	Question
	A radioactive decay chain starts from $_{93}N{p^{237}}$ and produces $_{90}T{h^{229}}$ by successive emissions. The emitted particles can be
	The half-life of a sample of a radioactive substance is 1 hour. If $8 \times {10^{10}}$ atoms are present at $t = 0$, then the number of atoms decayed in the duration $t = 2$ hour to $t = 4$ hour will be
	Carbon dating is best suited for determining the age of fossils if their age in years is of the order of
	A count rate meter shows a count of 240 per minute from a given radioactive source. One hour later the meter shows a count rate of 30 per minute. The half-life of the source is
	The half-life of radium is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after
	Activity of radioactive element decreased to one third of original activity ${R_0}$ in 9 years. After further 9 years, its activity will be
	The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant
	The half-life of a radioactive substance is 3.6 days. How much of 20 mg of this radioactive substance will remain after 36 days
	A radioactive material has a half life of 10 days. What fraction of the material would remain after 30 days
	Starting with a sample of pure $^{66}Cu,\,\frac{7}{8}$ of it decays into Zn in 15 min. The corresponding half-life is