Physics Nuclear Physics MDCAT 2013
PMDC Verified Question 80 of 98
Which one of the following emissions takes place in a nuclear reaction? $$ _{90}\text{Th}^{234} \rightarrow _{91}\text{Pa}^{234} + \_\_\_\_\_\_ $$
A
Alpha
B
Beta
C
Gamma
D
Photons
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Beta


Concept:

By analyzing the changes in atomic number (\(Z\)) and mass number (\(A\)) between the parent and daughter nuclei, we can identify the emitted particle.

Solution:

  • Parent nucleus: Thorium (\(Z=90, A=234\)).


  • Daughter nucleus: Protactinium (\(Z=91, A=234\)).


  • The mass number \(A\) remained 234. The atomic number \(Z\) increased from 90 to 91 (\(+1\)).


  • A process where \(Z\) increases by 1 and \(A\) is unchanged is the emission of an electron, which is a beta (\(\beta^{-}\)) particle.


Why other options are incorrect:

Alpha emission would decrease mass by 4. Gamma emission would not change \(Z\) or \(A\).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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