Student Login

Home›Chapters›Nuclear Physics PYQs›Law of Radioactive Decay›Question 90

NEET 2016 (Phase 2) · Law of Radioactive Decay

Law of Radioactive Decay question from NEET 2016 (Phase 2)

Q90NEET 2016 · PHASE 2Medium

Law of Radioactive Decay

The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is

Show answer and solution

Answer: (d)

40% decay leaves 60%; 85% decay leaves 15%.
$\frac{60}{15} = 4 = 2^2$ , so the gap is 2 half-lives.
$\Delta t = 2\times30 = 60$ min, so the answer is (d) 60.

Report a mistake

More questions on Law of Radioactive Decay

Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes…JEE Main 2016
Let N β be the number of β particles emitted by 1 gram of Na24 radioactive nuclei (half…JEE Main 2015 (11 Apr, Shift 1)
A radioactive X with a half life 1.4 × 109 years decays to Y which is stable. A sample of…NEET 2014 (AIPMT)
A piece of wood from a recently cut tree shows 20 decays per minute. A wooden piece of…JEE Main 2014 (19 Apr, Shift 1)
A piece of bone of an animal from a ruin is found to have 14C activity of 12…JEE Main 2014 (12 Apr, Shift 1)
A radioactive nuclei with decay constant 0.5/s is being produced at a constant rate of…JEE Main 2014 (11 Apr, Shift 1)
The half life of a radioactive isotope 'X' is 20 years. It decays to another element 'Y'…NEET 2013
The half-life of a radioactive element A is the same as the mean-life of another…JEE Main 2013 (22 Apr, Shift 1)