1. Search for Order Ancient Greeks: Aristotle Earth Air Fire Water
By 1800 Dalton suggested matter consisted of atoms
By 1936 atoms consist of the subatomic particles protons, neutrons, and electrons.
The electron, proton and neutron were thought to be the basic building blocks of matter.

2. Three laws must be conserved in all interactions between matter.
Conservation Laws
Three laws must be conserved in all interactions between matter.
Momentum
Mass/Energy
Charge

3. Momentum seemed not to be conserved in Beta decay.
In Beta decay momentum was seen to not be conserved.
Momentum seemed not to be conserved in Beta decay.

4. Proposed by Wolfgang Pauli in 1930.
Difficult to detect as they have no charge and very little mass.
Millions pass through your body each minute without any effect.

5. Conservation of Mass Energy
Einstein proposed that mass and energy were simply different ways of looking at the same thing.
Mass can turn to energy and vice versa.
He proposed that the amount of energy created from mass is found using the formula E = mc2

6. The Cockroft Walton experiment
Hydrogen nuclei were bombarded at a Lithium target.
Two alpha particles were produced in opposite directions. This conserved momentum.
The mass lost was equal to the energy gained.

9. Types of accelerator
An accelerator accelerates charge particle through very high voltages. Types Linear – Speeds are restricted by the length of the accelerator. The cathode ray tube is a linear accelerator. Circular – Speeds can increase with each revolution and focussing magnets keep the particles in position.

12. Pair production occurs when high energy photons pass close to a nucleus. The photon disappears and is replaced by 2 particles of oppostite charge(charge conservation) and moving in opposite directions(momentum conserved).

13. Pair Production
hf = 2mc2 + Ek1 +Ek2

14. Pair Annihilation

15. Pair Annihilation
e+ + e hf
Electron + Positron Gamma Rays

16. The Particle Zoo Accelerators allowed high speed collisions.
This resulted in the creation of a huge range of particles-the particle zoo.
Some of these particles
Pions formed by collision of proton and antiproton
Muons created by the decay of pions
When a photon strikes a H nucleus it creates a neutral lambda hyperon and a K meson.
Pions are a particle and an antiparticle.

17. The Gravitational Force
Weak
Acts on all particles
Infinite range
Only attractive

18. Stronger than gravity Acts on all particles Short range
The Weak Nuclear Force
Stronger than gravity
Acts on all particles
Short range
Found in beta decay

19. The Electromagnetic Force
Stronger than the weak force
Acts on charged particles
Infinite range
Binds atoms and molecules

20. The Strong Nuclear Force
Strongest force
Acts on protons and neutrons
Short range
Binds the nucleus

21. Forces in order of strength
Strong force
Electromagnetic force
Weak force
Gravitational Force
In other words
S E W G b

23. Leptons Light Particles Do not feel the strong nuclear force
Fundamental Particle
Examples - Electron, Muon, Tau

25. 2. BARYONS
Heavy Particles
Feel all forces
Examples are
neutron
proton

26. 3.Mesons
Intermediate mass
Feel all forces
Short lived
Example
Pion

27. Quarks neutron = u d d proton = u u d up u 2/3 down d -1/3 charm c
strange s
top t
bottom b
neutron = u d d
proton = u u d