Student Login

Home›Chapters›Nuclear Physics PYQs›Law of Radioactive Decay›Question 97

NEET 2013 · Law of Radioactive Decay

Law of Radioactive Decay question from NEET 2013

Q97NEET 2013Easy

Law of Radioactive Decay

The half life of a radioactive isotope 'X' is 20 years. It decays to another element 'Y' which is stable. The two elements 'X' and 'Y' were found to be in the ratio 1: 7 in a sample of a given rock. The age of the rock is estimated to be

Show answer and solution

Answer: (d)

$N_0 = N_X + N_Y$ , so $\frac{N_X}{N_0} = \frac{1}{1+7} = \frac{1}{8} = \left(\frac{1}{2}\right)^3$ .
Age $= 3\times20 = 60$ years.
So the answer is (d) 60 years.

Report a mistake

More questions on Law of Radioactive Decay

The half-life of a radioactive element A is the same as the mean-life of another…JEE Main 2013 (22 Apr, Shift 1)
The half life of a radioactive nucleus is 50 days. The time invertal (t2 - t1) between…NEET 2012 (AIPMT, Mains)
A mixture consists of two radioactive materials A1 and A2 with half lives of 20 s and 10…NEET 2012 (AIPMT, Prelims)
The half life of a radioactive isotope X is 50 years. It decays to another element Y…NEET 2011 (AIPMT, Prelims)
The half life of a radioactive substance is 20 minutes. The approximate time interval (t₂…JEE Main 2011 (AIEEE)
Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus R. At time…NEET 2011 (AIPMT, Mains)
The decay constant of a radio isotope is λ. If A1 and A2 are its activities at times t1…NEET 2010 (AIPMT, Mains)
The activity of a radioactive sample is measured as N0 counts per minute at t = 0 and…NEET 2010 (AIPMT, Prelims)