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Nuclear properties and  the radioactive decay law IB DP Physics Study Notes

Nuclear properties and  the radioactive decay law IB DP Physics Study Notes - 2025 Syllabus

Nuclear properties and  the radioactive decay law IB DP Physics Study Notes

Nuclear properties and  the radioactive decay law IB DP Physics Study Notes at  IITian Academy  focus on  specific topic and type of questions asked in actual exam. Study Notes focus on IB Physics syllabus with Students should understand

  • the existence of the strong nuclear force, a short-range, attractive force between nucleons

  • the activity, count rate and half-life in radioactive decay

  • the changes in activity and count rate during radioactive decay using integer values of half-life

  •  the effect of background radiation on count rate.

Standard level and higher level: 7 hours
Additional higher level: 5 hours

IB DP Physics 2025 -Study Notes -All Topics

Nuclear reactions

 

  •  The first induced nuclear reaction was accomplished by none other than Australian physicist Ernest Rutherford, the same guy who bombarded atoms with alpha particles and discovered the nuclear structure of the atom.
  •  From his experience with alpha emitters, Rutherford thought that alpha particles might just be energetic enough to breach the nuclear boundary.
  •  In fact, he did just that in the following nuclear reaction:

FYI

  •  The nuclear reaction above is an example of an artificial (induced) transmutation – where one element is transmuted into another through artificial means. It is alchemy!
  • Here is another induced transmutation that has been successfully accomplished:
  •   

FYI

  • At last man’s striving in the studies of alchemy have come to fruition! Recall what a driving force this was in chemistry and physics…
  • Particle accelerators are required.
  • But don’t go home asking mom for one so you can make your own bootleg gold.
  • Both accelerators and energy costs far outweigh the return in gold!

Here is an example of a nuclear equation:

There are two conservation laws used to balance a nuclear equation:
1. The conservation of nucleons tells us that the top numbers must tally on each side of the reaction.
2. The conservation of charge tells us that the bottom numbers must tally on each side of the reaction.

EXAMPLE:

Carbon-14 undergoes β decay to become nitrogen-14. Construct and balance the nuclear equation.

SOLUTION:

  •  Write the given information down and continue.
  •  From the conservation of nucleon number, we see that the electron has a nucleon number of 0.
  •  From the periodic table, we see that Z = 6 for carbon and Z = 7 for nitrogen.
  •  From the conservation of charge, we see that the charge of the beta particle must be -1.
  •  Finally, don’t forget the antineutrino for β⁻ decay.

The unified atomic mass unit

  •  In the world of nuclear reactions, we have to keep very precise track of the mass of the nuclei if we are to determine the energy of a reaction.
  •  To this end, we define the unified atomic mass unit (u) using a neutral carbon-12 atom as our standard of precisely 12.000000 u.

EXAMPLE:

How many AMUs is 25.32 g of anything?

▶️Answer/Explanation

SOLUTION:
\[
(25.32 \, \text{g})(\frac{1 \, \text{kg}}{1000 \, \text{g}})(\frac{1 \, \text{u}}{1.661 \times 10^{-27} \, \text{kg}}) = 1.524 \times 10^{25} \, \text{u}.
\]

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