Physics Nuclear Physics NUMS 2020
PMDC Verified Question 51 of 98
\( 4.5 \times 10^9 \) year is the half-life of:
A
\(\text{U}^{238}\)
B
\(\text{U}^{235}\)
C
\(\text{U}^{236}\)
D
\(\text{U}^{234}\)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \(\text{U}^{238}\)


Concept:

This is a standard memorization question regarding the primordial isotopes crucial for Earth's radiometric dating.

Solution:

  • Uranium-238 (\(\text{U}^{238}\)) is the most abundant natural isotope of Uranium and has a highly stable, immensely long half-life of \(4.468 \times 10^9\) years (often rounded to \(4.5 \times 10^9\) in textbooks).


  • This duration closely mirrors the physical age of the Earth, making U-238 essential in geological age-dating.


Why other options are incorrect:

U-235 has a much shorter half-life of about 700 million years. U-234 has a half-life of 245,000 years.

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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