A) 0.36 MeV
B) 0.41 MeV
C) 0.48 MeV
D) 1.32 MeV
Correct Answer: A
Solution :
Rest mass energy of electron \[=0.54\text{ }MeV\] i.e., \[{{m}_{0}}{{c}^{2}}=0.54\,MeV\] ...(i) But the kinetic energy of electron \[=m{{c}^{2}}={{m}_{0}}{{c}^{2}}\] ?(ii) Also, \[m=\frac{{{m}_{0}}}{\sqrt{1-\frac{{{v}^{2}}}{{{c}^{2}}}}}\] \[=\frac{{{m}_{0}}}{\sqrt{1-{{(0.8)}^{2}}}}=\frac{{{m}_{0}}}{0.6}\] So, \[m{{c}^{2}}=\frac{{{m}_{0}}{{c}^{2}}}{0.6}\] \[=\frac{0.54}{0.6}\,\text{MeV}\] [From Eq (i)] \[m{{c}^{2}}=0.9\,MeV\] ?(ii) Substituting values of Eq (ii) and (i) in Eq (ii), we get \[KE=(0.9-0.54)MeV=0.36\,MeV\]
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