AP Physics

1. Chapter 31
Nuclear Physics and
Radioactivity

2. 31.1 Nuclear Structure
The atomic nucleus consists
of positively charged protons
and neutral neutrons.

3. 31.1 Nuclear Structure

neutrons
ofNumber
protons
ofNumber
neutronsand
protonsofNumber
NZA +=
atomic
number
atomic mass
number

4. 31.1 Nuclear Structure
Nuclei that contain the same number of protons but a different
number of neutrons are known as isotopes.

5. 31.1 Nuclear Structure
( ) 3115
m102.1 Ar −
×≈

6. 31.2 The Strong Nuclear Force and the Stability of the Nucleus
The mutual repulsion of the protons
tends to push the nucleus apart. What
then, holds the nucleus together?
The strong nuclear force.

7. 31.2 The Strong Nuclear Force and the Stability of the Nucleus
As nuclei get larger, more
neutrons are required for
stability.
The neutrons act like glue
without adding more repulsive
force.

8. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy
( ) ( ) 22
deficitMassenergyBinding cmc ∆==

9. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy
Example 3 The Binding Energy of the Helium Nucleus Revisited
The atomic mass of helium is 4.0026u and the atomic mass of hydrogen
is 1.0078u. Using atomic mass units, instead of kilograms, obtain the
binding energy of the helium nucleus.

10. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy
u0304.0u0026.4u0330.4 =−=∆m
MeV5.931u1 ↔
MeV3.28energyBinding =

11. 31.3 The Mass Deficit of the Nucleus and Nuclear Binding Energy

12. 31.4 Radioactivity
A magnetic field separates three types of particles emitted by
radioactive nuclei.

13. 31.4 Radioactivity
α DECAY
HeDP 2
2
4
2 +→ −
−
A
Z
A
Z

14. 31.4 Radioactivity
A smoke
detector

15. 31.4 Radioactivity
β DECAY
eDP 0
11 −+ +→ A
Z
A
Z

16. 31.4 Radioactivity
γ DECAY
γPP +→∗ A
Z
A
Z
excited energy
state
lower energy
state