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# Take out hwk & tables. PowerPoint PPT Presentation

Take out hwk & tables. Compare answers to hwk sets. List 2 pieces of evidence that light is a wave. Diffraction Interference. List 1 piece of evidence that light is a stream of particles. Photoelectric effect. List 1 piece of evidence for the Bohr model of the atom.

Take out hwk & tables.

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## Take out hwk & tables.

List 2 pieces of evidence that light is a wave.

• Diffraction

• Interference.

List 1 piece of evidence that light is a stream of particles.

• Photoelectric effect

List 1 piece of evidence for the Bohr model of the atom.

• Emission or Absorption spectra

### Ref Table Page 3.

Standard Model

• Physicists have developed a theory called “The Standard Model” that explains what the world is and what holds it together.

### Standard Model

• It was once thought that the fundamental particles were electrons, protons, neutrons.

• Now more & smaller subatomic particles found – quarks & leptons that comprise matter.

• Forces are carried by particles too!

p+ & no

Quarks can’t exist alone.

### Protons, Neutrons: are baryons made of only up & down quarks.

• Ex 1. How many up & down quarks in a p+?

• Charge = +1

• Baryons have 3 quarks only.

• 2 up & 1 down.

• u + u + d

• +2/3 +2/3 – 1/3 = +1

• Ex 2: How many up & down quarks in a no?

• Charge = 0

• 1 up & 2 down.

• u d d

• +2/3 -1/3 -1/3 = 0

### Leptons

• The most familiar member of this group is the electron e, but there are also heavier particles called the muon m and the tau t.

• For each of those, there is a smaller “partner” called a neutrino n .

• The leptons are all capable of independent existence.

### All particles have anti-particles same mass.

• Antiparticles behave same as corresponding matter particles, except they have opposite charges.

• A proton is electrically positive - an antiproton is negative.

• Gravity affects matter and antimatter the same way.

• If matter & corresponding antimatter meet, they annihilate into pure energy!

### 3. A particle is composed of 2 charm, & 1 bottom quark.

• What type of particle is it?

• Write the symbols & charges for all the particles.

• c c b

• +2/3+2/3-1/3

What is its charge?

• +1.

### 4. A particle is composed of 1 anti-strange, & 1 down quark.

• Write the symbols & charges for all the particles.

• What type of particle is it?

• s d

• +1/3-1/3

What is it’s charge?

• 0.

• Meson.

### Forces & Force Exchange Particles4 Fundamental Forces

The universe exists because the fundamental particles interact. These interactions include 4 attractive & repulsive forces, decay, & annihilation.

Force particles are gaugebosons.

• Strong Nuclear (Nuclear)

• Electromagnetic

• Weak (Nuclear)

• Gravity

### Strong Force

• Short Range, Attractive only – holds nuclear particles together.

• Particle = gluons.

### Electromagnetic Force

• Long range. Attracts & repels charged particles (Coulomb’s Law).

• Carrier particle = photon.

### Weak Force

• In the nucleus. Involved with decay of particles. Short range.

The carrier particles of the weak interactions are the W and Z bosons.

### Gravity

• Long range weakest force. Attractive only.

• The gravity force carrier particle has not been found. It, however, is predicted to exist and may someday be found: the graviton.

## Quarks & Leptons 5:40 min.http://www.youtube.com/watch?v=aTFCKbZw8QY

Hwk:

Do pg 923 #1,2 Pg 928 #30 – 37 Full sentences!

2. Bring back textbook!

Summary:

• EM energy can be thought of as tiny particles (photons) related to f.

• E in EM radiation/photons E = hf.

• Matter can be thought of as E stored in nucleus.

• E in matter E = mc2. Joules.

• 1 u = 931 MeV. 1 x 106eV = 1 MeV.

• E measured in eV and J.

• 1.6 x 10-19 J = 1 eV .

The charge on the quark below would be:

• +1

• -1

• +2/3

• -2/3

This particle is a:

• Lepton

• Proton

• Meson

• neutron