1. Modern Physics Wave-Particle Duality Model of the atom
Radioactivity / Four Forces of nature

2. Wave-Particle Duality
When tested as if it were a wave, light behaves like a wave. Light will:
Diffract
Refract
Exhibit interference
Polarize
exhibit the Doppler effect (ex. Red shift)
When tested as a particle, light behaves like a particle (ex. the photoelectric effect).

3. The nucleus of the atom
The neutrons and protons are grouped together in the nucleus, which is at the center of the atom.
If the atom were the size of your classroom, the nucleus would be the size of a single grain of sand in the center of the room.
Most of an atom’s mass is concentrated in the nucleus.

4. Scientists describe all of nature with only four forces.
Gravitational force
Weak Nuclear force
Electromagnetic force
Strong nuclear force
It is important to note that scientists do no know why these forces exist or what causes them. We only observe their effects and propose they are there.

5. Electromagnetic Force
The force is the attraction between protons (positive) and electrons (negative).
Electrons are bound to the nucleus by electromagnetic forces.
The momentum of the electron causes it to move around the nucleus rather than falling straight in.

6. Strong Nuclear Force Holds the nucleus of an atom together
Attracts neutrons and protons to each other, otherwise the positively charged protons would repel each other.

7. Weak Nuclear Force
Causes a neutron to break into a proton and an electron producing a new element
Weaker than both the electric force and the strong nuclear force.
Causes radioactive decay
Only occurs at the subatomic level
The force of gravity causes objects to be attracted to each other
Every process we know in the universe can be explained in terms of these fundamental forces.

8. Marie Curie – Nobel prize winner
The word radioactivity was first used by Marie Curie in 1898.
She used the word radioactivity to describe the property of certain substances to give off invisible “radiations” that could be detected by films.

9. Radioactive Decay
Three different kinds of radiation given off by radioactive materials:
Alpha rays
Beta rays
Gamma rays
called “rays” because the radiation carried energy and moved in straight lines, like light rays.

10. Radioactivity comes from the nucleus of the atom.
If the nucleus has too many neutrons, or is unstable the atom undergoes radioactive decay.
decay - to "break down."

11. Atomic Decay
Alpha decay: the nucleus ejects two protons and two neutrons.
Beta decay: a neutron in the nucleus splits into a proton and an electron.
Gamma decay occurs because the nucleus is at too high an energy. The nucleus falls down to a lower energy state and, in the process, emits a high energy photon.

12. Radioactive decay gives off energy.
The energy comes from the conversion of mass into energy.
Because the speed of light (c) is such a large number, a tiny bit of mass generates a huge amount of energy.
Radioactivity occurs because everything in nature tends to move toward lower energy.

13. Radiation The flow of energy through space. Forms of radiation:
Light
Radio
Microwaves
X-rays
Many people mistakenly think of radiation as only associated with nuclear reactions.

14. X-ray machines X-rays are photons
Used to produce images of bones and teeth on x-ray film.
X-ray film turns black when exposed to x-rays.

15. X-Rays Uses
High level therapeutic x-rays are used to destroy diseased tissue, such as cancer cells.
The beams are made to overlap at the place where the doctor wants to destroy diseased cells.

16. CAT scan Computerized Axial Tomography
Produced by a computer that controls an x-ray machine as it takes pictures of the body from different angles.
Produces three-dimensional images of bones and other structures within the body.

17. Radiation oncology is the medical specialty concerned with prescribing radiation therapy in treatments for cancer, and is distinct from radiology, the use of radiation in medical imaging and diagnosis. 
Radiologists use an array of imaging technologies (such as X-ray radiography, ultrasound, computed tomography (CT), nuclear medicine, positron emission tomography (PET) and magnetic resonance imaging (MRI) to diagnose or treat diseases.

18. Radiation Detection
The Geiger counter is a type of radiation detector invented to tell when radiation is present and to measure its intensity.
A Geiger counter detects radiation by electrically collecting ions of gas.
The cylinder is positive and the wire in the center is negative.
Ionizing radiation knocks electrons from molecules of gas in the cylinder.
The ions and electrons make an electric current that is proportional to the intensity of the radiation.

19. Fusion reactions
Nuclear reaction that combines, or fuses, two smaller nuclei into a larger nucleus.
It is difficult to make fusion reactions occur because positively charged nuclei repel each other.

20. Fission reactions
A fission reaction splits up a large nucleus into smaller pieces.
A fission reaction typically happens when a neutron hits a nucleus with enough energy to make the nucleus unstable.

21. Nuclear Reactions and Energy
A nuclear reaction is any process that changes the nucleus of an atom.
Radioactive decay is one form of nuclear reaction.

22. Nuclear Reactions and Energy
If you could take apart a nucleus and separate all of its protons and neutrons, the separated protons and neutrons would have more mass than the nucleus did.
The mass of a nucleus is reduced by the energy that is released when the nucleus comes together.
Nuclear reactions can convert mass into energy.

23. Nuclear Reactions and Energy
Both these nuclear reactions release a small portion of the mass as large amounts of energy.
Nuclear fusion is what powers a modern nuclear warhead.
Nuclear fission (less powerful) occurs in an atomic bomb (like the ones used against Japan in WWII), or in a nuclear power plant.

24. E = mc2 E m c2 Mass Energy Equivalence
The energy released can be calculated using the equation: E m c2
E = mc2
Where:
E = energy released (J)
m = mass difference (kg)
c = speed of light in a vacuum (3 x 108 m/s)

25. Practice Problem 1: The energy equivalent of 8.9x10-7 kg is…..
Remember the formula is E = mc2
C is the speed of light
8.01x1010 J

26. Practice Problem 2:
The energy released is equal to 9.6x1014 J. What was the original mass?
Remember the formula is E = mc2
Manipulate the formula to find mass
E/c2 = m
C is the speed of light
kg or x10-2kg