JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2004

  • question_answer
        For thorium A = 232, Z = 90 at the end of some radioactive disintegration we obtain an isotope of lead with A = 208 and Z = 82, then the number of emitted a and P particles are :

    A) \[\mu =\text{1}.\text{33}\]        

    B)  \[\text{1}.\text{5}\times \text{1}{{0}^{\text{8}}}\text{ km}\]

    C) \[\text{5}\times \text{1}0{{~}^{14}}\text{Hz}\]                

    D)  \[\text{55}00\text{ { }\!\!\mathrm{\AA}\!\!\text{ }}\]

    Correct Answer: C

    Solution :

                    Given \[_{90}T{{h}^{232}}{{\to }_{82}}P{{b}^{208}}\]                       ??(1) Change in mass number \[=\text{ 232 }-\text{ 2}0\text{8 }=\text{ 24}\] No. of \[\alpha \]-particles emitted \[=\frac{24}{4}=6\] Now equation (1) becomes \[_{90}T{{h}^{232}}{{\xrightarrow{-6\alpha }}_{78}}P{{b}^{208}}{{\xrightarrow{-n\beta }}_{82}}p{{b}^{208}}\] Further change in atomic number is \[82-78=4\] It means atomic no. 78 is increased by 4 to make the atomic no. 82. Therefore 6a-parUcles and 4\[\beta \]-particles will be emitted..


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