KVPY 2019 SB SX Exam Previous Papers

Question : 37 of 120

Marks: +1, -0

Originally the radioactive beta decay was thought as a decay of a nucleus with the emission of electrons only (case I). However, in addition to be electron, another (nearly) massless and electrically neural particle is also emitted (Case II). Based on the figure below, which of the following is correct :

(a) in both cases I and II
(a) in case I and (b) in case II
(a) in case II and (b) in case I
(b) in both cases I and II

Validate

Solution:

β^{-}

decay occurs as

{ }_{Z}^{A} X ⟶{ }_{Z+1}^{A} Y+{ }_{-1}^{0} β+\ov{v}

Most of the decay energy is carried by both emitted electron

β^{-}

and antineutrino (

\ov{v}

).
So,

β^{-}

- particles emerges with varrying energies and energy spectrum of emitted

β^{-}

is as shown;

If there are no antineutrinos, energy is carried mainly by

β^{-}

- particles, so energy spectrum will be

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