1. Do Now
An electron in a hydrogen atoms drops from n=5 to n=4 energy level.
What is the energy of the photon in eV?
What is the frequency of the emitted photon?
What color (type) of light is this?

2. SWBAT discuss the standard model of particle physics
Monday, June 6th 2016

3. Four fundamental forces From strongest to weakest
Strong Nuclear Force: holds protons and neutrons together in the nucleus
Electromagnetic Force: electrical and magnetic attraction and repulsion
Weak force: responsible for radioactive beta decay (neutrons break apart)
Gravitational Force: attractive force between objects with mass
Need to know: You should be able to identify what each type of force does.

4. Holds atoms and molecules together Holds objects with mass together
Fundamental Forces
Force
Range
Strength
Carrier
What it does
Strong Nuclear
10-15 m 1
gluons
Holds nuclei together
Electromagnetism
Infinite
1/137
photons
Holds atoms and molecules together
Weak Nuclear
10-18 m
10-6
W & Z bosons
beta decay
Gravity
10-39
graviton?
Holds objects with mass together

5. Fundamental Forces
These four forces govern all known interactions in the universe.
They work through the exchange of “carrier particles”
Look below, each force has a “carrier” particle
Eg: the exchange of photons, creates electromagnetic force
For this, all you need to know is how to read a chart like this to determine which particle carries which type of force.

6. Fundamental forces
The exchange of which carrier particle(s) create the strong nuclear force?
Exchange of gluons creates the strong nuclear force.

7. The standard model
All particles are classified by the type of force interactions they have.
Hadrons: protons and neutrons ( interact using all 4 types of force)
Leptons: electrons, positrons, neutrinos (do NOT interact with strong force)
Need to know: protons and neutrons are hadrons and electrons are leptons. You don’t have to fully understand these classifications.

8. Hadrons
All hadrons are made of smaller particles called QUARKS. These quarks belong to one of two categories:
baryons: includes proton and neutron; baryons are made up of three quarks
Mesons: made up of a quark and an antiquark (anti just means the negative version of a quark)
Look at page 5 of your reference table. More information about quarks is available there. Anti-quarks are quarks with a negative overall charge.

9. Hadron question
What is the total number of quarks in a Helium nucleus which contains 2 protons and 2 neutrons?
Hint: look at the previous slide to see the number of quarks in a proton.
12 quarks (3 for each proton and 3 for each neutron)

10. The Standard Model of Particle Physics
Quark: indivisible particle that makes up protons and neutrons (hadrons)
6 types, listed on Reference Table page 3:
On this chart, little e stands for elementary charge. So each quark contains a fraction of the elementary charge (1.6x10-19C) These quarks cannot exist without their partners so the smallest unit of charge is still just e.

11. Using the standard model to find the make-up of protons and neutrons.
Proton: up, up, down (quarks
+2/3e + +2/3e + -1/3e =+1e
This says that protons are made of three quarks which add up to 1e (or 1.6x10-19C)
Neutron: up, down, down
+2/3c + -1/3e + -1/3e = 0e
This makes sense because neutrons have no charge
All you need to be able to do is add fractions together. We know that the charge on a proton is one elementary charge (1e) so the quarks in a proton add up to 1.

12. Particle composition
What is the electric charge on a particle having a quark composition of down, strange, and bottom?
Remember, it’s just adding fractions.
(-1/3e + -1/3e + -1/3e) = -1e

13. Particles that are not made up of quarks are called leptons, and electrons are the most common example. Leptons are indivisible.
Electrons are not made up of smaller particles. They have the same elementary charge as a proton (1e) but the opposite of the proton which is why they have a negative in front of their charge, -1e.

15. Antimatter has been observed, and every particle has an antiparticle that is identical to the original but with opposite charge
Eg: an antiproton is a baryon that has the same mass as a proton but -1e charge
Eg: a positron is identical to an electron but with an opposite charge (+1e)

16. Antimatter collisions
The diagram shows a picture of a proton/antiproton collision.
Is the total charge of all particles before and after the collision the same?

17. Beta Decay
A neutron will spontaneously decay into a proton, electron, and anti-electron neutrino.
- udd  uud
(one down quark becomes an up quark)
- charge is conserved
- mass of neutron > mass of proton

18. Example Questions
Give one example of a hadron and one example of a lepton.
The three quarks that make up a proton should add up to what number?
A particle has a quark composition of down, down, strange (dds.) What is the charge on the particle? Is it a meson or baryon?