**NUCLEI QUIZ-6**

**NUCLEI QUIZ-6**

**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.

**Q2. Some radioactive nucleus may emit**

Solution (a)
No radioactive substance emits both Î± and Î² particles simultaneously. Some substances emit Î±-particles and some other emits Î²-particles, Î³-rays are emitted along with both Î± and Î²-particles

**Q3A radioactive sample consists of two distinct species having equal number of atoms initially. The mean lifetime of one species is Ï„ and that of the other is 5Ï„. The decay products in both cases are stable. A plot is made of the total number of radioactive nuclei as a function of time. Which of the following figures best represents the form of this plot?**

**Q4 Atomic mass number of an element is 232 and its atomic number is 90. The end product of this radioactive element is an isotope of lead (atomic mass 208 and atomic number 82). The number of Î±- and Î²-particles emitted are**

Solution
(b)
Number of Î±-particles emitted =(232-208)/4=6
Decrease in charge number due to Î±-emission = 12
But actual decrease in charge number =90-82=8
Clearly, four Î²-particles are emitted

**Q5. The compound unstable nucleus _92^236 U often decays in accordance with the following reaction _92^236 U→ _54^140 Xe+ _38^94 Sr+ order particles In the nuclear reaction presented above, the ‘other particle’ might be**

Solution (d)
Nuclear reactions conserve total charge, and also conserve the total approximate mass. The other particles in the reaction will have mass =236-140-94=2
The other particles are two neutrons. Hence, (a) is not correct.
For nuclei, number of protons tells the charge. So, the other particles must have charge Z such that
92=54+38+Z
∴Z=0
Therefore, the other particles have a total atomic mass 2 and total charge 0. Hence, only (d) is correct

**Q7. Consider Î±-particles, Î²-particles and Î³-rays, each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are:**

Solution
(c)
The penetrating power is dependent on velocity. For a given energy, the velocity of Î³-radiation is highest and Î±-particle is least

**Q8. If in nature there may not be an element for which the principle quantum number n>4, then the total possible number of elements will be**

Solution
(a)
For n=1, maximum number of states =2n^2=2 and for n=2,3,4, maximum number of states would be 8, 18, 32 respectively, Hence number of possible elements
=2+8+18+32=60

**Q9A freshly prepared radioactive source of half-life 2 h emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with the source is**

**Q10. In the nuclear reaction given by _2 He^4+〖 _7 N〗^14→〖 _1 H〗^1+X, the nucleus X is**

Solution

(d)
Use mass balance and balance of atomic number