NCERT Class XII Chapter
Nuclei
Questions With Solutions
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Question : 14
Total: 31
The nucleus
N e decays by β – emission. Write down the β – decay equation and determine the maximum kinetic energy of the electrons emitted. Given that:
m(
N e ) = 22.994466 amu, m (
N a ) = 22.989770 amu
m
Solution:
The β – decay of
N e may be explained as
N e →
N a +
e +
+ Q
The expression or the kinetic energy released may be written as
Q =[ m (
N e ) − m (
N a ) − m e ] c 2 = [ m (
N e ) − m (
N a ) ] c 2
≈ [22.994466 – 22.989770] × 931.5 MeV
≈ 0.004696 × 931.5 MeV = 4.374 MeV
As
N a is massive, the kinetic energy released is mainly shared by electron-positron pair. When the neutrino carries no energy, the electron has a maximum kinetic energy equal to 4.374 MeV.
The expression or the kinetic energy released may be written as
Q =
≈ [22.994466 – 22.989770] × 931.5 MeV
≈ 0.004696 × 931.5 MeV = 4.374 MeV
As
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