Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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# The Masses of 11c and 11b Are Respectively 11.0114 U and 11.0093 U. Find the Maximum Energy a Positron Can Have in the β*-decay of 11c to 11b. - Physics

#### Question

The masses of 11C and 11B are respectively 11.0114 u and 11.0093 u. Find the maximum energy a positron can have in the β*-decay of 11C to 11B.

(Use Mass of proton mp = 1.007276 u, Mass of ""_1^1"H" atom = 1.007825 u, Mass of neutron mn = 1.008665 u, Mass of electron = 0.0005486 u ≈ 511 keV/c2,1 u = 931 MeV/c2.)

#### Solution

Given:-
Mass of 11C, m(11C) = 11.0114 u
Mass of 11B, m(11B) = 11.0093 u
Energy liberated in the β+ decay (Q) is given by

Q = [m(""^11C) - m(""^11B) - 2m_e]c^2

= (11.0114 u − 11.0093 u - 2 × 0.0005486 u)c2

= 0.0010028  × 931 MeV

= 0.9336 MeV = 933.6 keV

For maximum KE of the positron, energy of neutrino can be taken as zero.

∴ Maximum KE of the positron = 933.6 keV

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Solution The Masses of 11c and 11b Are Respectively 11.0114 U and 11.0093 U. Find the Maximum Energy a Positron Can Have in the β*-decay of 11c to 11b. Concept: Radioactivity - Law of Radioactive Decay.
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