Q 12-13-141JEE MainJEE Main 2025 (4 Apr, Shift 2)Easy
A radioactive material P first decays into Q and then Q decays to non-radioactive material R. Which of the graphs shown in the figure represents the time-dependent mass of P, Q and R?
Answer: (B) Graph (2)
- P only decays, so its mass falls steadily (exponentially) from its initial value.
- Q starts at zero, grows while P feeds it, then falls as it decays faster than it is produced, so it rises to a peak and then decreases.
- R is stable and only accumulates: it starts at zero and rises, levelling off at the end.
Only graph (2) shows P falling, Q rising and then falling, and R rising to a steady value.
Solution by Sreeraj P, M.Sc Physics