**NUCLEI QUIZ-11**

**NUCLEI QUIZ-11**

**Dear Readers,**

JEE Advanced Physics Syllabus can be referred by the IIT aspirants to get a detailed list of all topics that are important in cracking the entrance examination. JEE Advanced syllabus for Physics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with day-to-day experiences. In comparison to the other two subjects, the syllabus of JEE Advanced for physics is developed in such a way so as to test the deep understanding and application of concepts.

**Q1.If the decay or disintegration constant of a radioactive substance is Î», then its half life and mean life are respectively**

Solution

**Q2. Rank the following nuclei in order from largest to smallest value of the binding energy per nucleon: (i) _2^4 He , (ii) _24^52 Cr, (iii) _62^152 Sm, (iv) _80^100 Hg, (v) _92^252 Cf**

Solution

(c)
The binding energy per nucleon is lowest for very light nuclei such as _2^4 He, is greatest around A=60, and then decreases with increasing A

**Q3 Plutonium has atomic mass 210 and a decay constant equal to 5.8×10^(-8) s^(-1). The number of Î±-particles emitted per second by 1 mg Plutonium is (Avogadro’s constant =6.0×10^23)**

**Q4 Neutron decay in the free space is given as follows:〖 _0 n〗^1→〖 _1 H〗^1+〖 _(-1) e〗^0+[ ] Then, the parenthesis represents**

Solution

(d)
The emission of antineutrino is a must for the validity of different laws

**Q5. U-235 can decay by many ways, let us here consider only two ways A and B. In decay of U-235 by means of A, the energy released per fission is 210 MeV while in B it is 186 MeV. Then, the uranium 235 sample is more likely to decay by**

Solution

(a)
Since scheme A releases more energy than scheme B, scheme A is more likely to occur. This is because the more the energy released, the more stable the daughter nucleus is. A heavy nucleus undergoes fission such that its products will be more stable than the parent nucleus

**Q6 The decay constant of a radioactive sample is Î». The half-life and mean-life of the sample are, respectively, given by**

Solution

**Q7. The half-life of ^131 I is 8 days. Given a sample of ^131 I at time t=0, we can assert that**

Solution

(d)
As we regard the decay process as a spontaneous and statistical process, therefore the decay can start any time after t=0. Therefore, the answer is (d)

**Q8 In the disintegration series _92^238 U□(→┴( Î± ) X〖□(→┴〖 Î²〗^- )〗_( Z)^( A) Y) The values of Z and A, respectively, will be**

Solution

(d)
Î±-decay decreases mass number by 4 and reduces charge number by 2. Î²-decay keeps mass number unchanged and increases charge by 1. Clearly, option (d) is the right choice

**Q9 The nuclear radius of _8 O^16 is 3×10^(-15) m. If an atomic mass unit is 1.67×10^(-27) kg, then the nuclear density is approximately?**

**Q10There are two radioactive substances A and B. Decay constant of B is two times that of A. Initially, both have equal number of nuclei. After n half-lives of A, rates of disintegration of both are equal. The value of n is**