The isotope `_(5)^(12) B` having a mass `12.014 u`undergoes beta - decay to `_(6)^(12) C _(6)^(12) C `has an excited state of the nucleus `( _(6)^(12) C ^(**) at 4.041 MeV` above its ground state if `_(5)^(12)E` decay to `_(6)^(12) C ^(**) ` , the maximum kinetic energy of the `beta` - particle in unit of MeV is `(1 u = 931.5MeV//c^(2)` where c is the speed of light in vaccuum) .

Answer

9

Explanation

`._(2)^(12)B rarr ._(6)^(12) C+ ._(-1)^(0)e+bar(v)`
Mass defect `=(12.014-12) u`
`:.` Released energy `=13.041 MeV`
Energy used for excitation of `._(6)^(12)C=4.041 MeV`
`:.` Energy converted to KE of electron
`=13.041-4.041=9` MeV