Physics Nuclear Physics UHS 2023
PMDC Verified Question 18 of 98
The decay rate of radioactive substance is:
A
Constant with time
B
Varies inversely with time
C
Decrease exponentially
D
Decreases linearly with time
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Decrease exponentially


Concept:

The rate of decay (Activity) depends strictly on the number of unstable nuclei present at any given moment.

Formula:

$$ A = A_0 e^{-\lambda t} $$

Solution:

  • Because nuclei are constantly decaying, the total number of remaining unstable nuclei continuously drops.


  • As the pool of available nuclei drops, there are fewer atoms available to decay in the next second.


  • This creates a mathematical curve where the decay rate decreases exponentially as time progresses.


Why other options are incorrect:

If it were constant, elements would vanish instantly at the end of their lifespan. Inverse and linear functions do not model the probabilistic nature of quantum decay.

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.

Previous Question All Nuclear Physics MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App