Chapter 1 Flashcards
What does an atom consist of?
Central positively charged nucleus containing protons and neutrons (nucleons)
What is the diameter of an atom? (Atomic diameter)
10^-10m
What surrounds the nucleus of an atom?
Electrons
What is the diameter of the nucleus of an atom?
10^-15m or 1 femtometer
What is the charge and relative charge of a proton?
1.6 x10^-19, +1
What is the charge and relative charge of a neutron?
0, 0
What is the charge and relative charge of a electron?
-1.6 x10^-19, -1
What is the symbol for proton/atomic number?
Z
What is the proton number equal to?
Number of protons in the nucleus of an atom
What is the symbol for mass/nucleon number?
A
What is the mass number equal to?
Number of protons + number of neutrons in the nucleus of an atom
What are isotopes?
Atoms with the same amount of protons and different numbers of neutrons
If 2 different atoms have the same proton number, they are of…?
The same element
Are all isotopes radioactive?
No
What are radioactive isotopes called?
Radioisotopes
What is the equation of specific charge?
charge of particle / mass of particle
Which out of protons, neutrons and electrons have the largest specific charge?
Electrons
Define the strong nuclear force
Stable isotopes have nuclei that don’t disintegrate. There must be a force holding them together
What does the strong nuclear force overcome in the nucleus?
Electrostatic force of repulsion between protons in the nucleus
What does the strong nuclear force do?
Keep protons and neutrons together
What is the range of the strong nuclear force?
3-4 femtometers (diameter of nucleus)
What is the range of electrostatic force? And when does the range start to decrease?
Infinite. Starts to decrease when the range between 2 charged particles increases
What distance does the strong nuclear force start to act as a repulsive force?
When distance is less than 0.5 femtometer
Why does the strong nuclear force turn into a repulsive force at very small distances?
To prevent protons and neutrons being pushed into each other. This prevents the nucleus collapsing intoa point
When is electromagnetic radiation emitted?
When charged particles lose energy
Give 2 examples when electromagnetic radiation would be emitted
- Electrons decreasing in energy inside an atom (light)
2. Electrons losing energy when stopped by a solid material (X-rays)
Name the electromagnetic spectrum in order of decreasing wavelengths/increasing frequency
Radio, microwave, infrared, visible, ultra violet, x-ray, gamma ray
What is the wavelength of a radio wave?
Greater than 0.1m
What is the wavelength of an microwave?
0.1mm-1mm
What is the wavelength of an infrared wave?
1mm to 700nm
What is the wavelength of visible light?
700nm to 400nm
What is the wavelength of an ultraviolet wave
400nm to 1nm
What is the wavelength of an x-ray?
less than 1nm
What is the wavelength of a gamma ray?
less than 1nm
Do all forms of radiation travel at the same speed through a vacuum?
Yes
What speed to all forms of radiation travel at in a vacuum?
3 x10^8m/s
What is a photon?
A packet of wave energy
How is EM radiation emitted?
As a short burst of waves in all directions
What does a photon contain?
A set amount of energy
Define antimatter
All particles of normal matter have a corresponding particle that:
- Has the same mass as the normal particle
- Has opposite charge (if normal particle is charged)
- Will undergo annihilation with normal particle if they meet
What is the antiparticle for a proton and what is it?
Anti proton - negatively charged proton
What is the antiparticle for a electron and what is it?
Positron - positively charged electron
Define annihilation
When particles and anti particles meet and their mass is converted into pure energy
Define the process of annihilation (what happens)?
A particle and anti particle meet, and all of their mass and KE turn into 2 photons of equal frequency that move off in opposite directions
How is pair production different to annihilation?
Annihilation - matter -> energy
Pair production - energy -> matter
Define the process of pair production (what happens)?
The energy of 1 photon can be used to create a particle and its corresponding antiparticle
How do photons conserve momentum?
By interacting with another particle
How many joules is 1 electron volt?
1eV = 1.5 x10^-19 J
How many joules is 1 mega electron volt?
1MeV = 1.5 x10^-13 J
How many electron volts is 1 joule?
1J = 1 / (1.6x10^-19) eV
What is an electron volt equal to?
The KE gained by an electron when accelerated by a p.d of 1V
What is the unit of sub atomic particles most commonly quoted as?
MeV
In pair production, what is always conserved?
Energy, momentum, charge, lepton number, baryon number, strangeness
What are virtual particles?
Virtual particles are exchanged when forces are experienced between particles
Where does the virtual particle travel?
Between real particles affecting their motion
What are exchange particles called which are transferred between fundamental particles
Gauge bosons
Describe what happens in a feynman diagram with the repulsion of 2 electrons?
2 electrons travel, then exchange a photon, and then 2 electrons travel off
State the equation for beta - decay
A A 0 _
X -> Y + B + Ve
Z Z + 1 -1
Describe what happens in a feynman diagram with Beta - decay
Neutron travels, exchanges a W - boson, turns into a proton, B- particle and anti electron neutrino
Describe what happens in a feynman diagram with the interaction of a neutron and anti neutrino
Neutron and neutrino travel, exchange a W - boson, turns into a proton and B- particle
What are neutrinos affected by?
Weak nuclear force
What forces don’t neutrinos feel?
Strong and electrostatic
Describe what happens in a feynman diagram with beta plus
Proton travels, exchanges a W+ boson, turns into neutron, positron and neutrino
Describe what happens in a feynman diagram with the interaction of a proton and anti-neutrino
Proton and neutrino travel, exchange W+ boson, turn into neutron and positron
Describe what happens in a feynman diagram with electron capture
Proton and electron travel, exchange W+ boson, turn into a neutron and neutrino
Describe what happens in electron capture
One of excess protons interacts with one of the inner shell electrons to form a neutron producing a neutrino
What are the 2 categories of matter and anti matter?
Hadrons and leptons
What are 2 sub-categories of hadrons?
Baryons and mesons
What are hadrons?
Particles that interact through strong interaction
What are leptons?
Particles that interact through weak interaction
What are baryons?
Hadrons that are protons that eventually decay into protons e.g protons, neutrons
What is a meson?
Hadrons that don’t include protons in decay product. All mesons are unstable e.g Pions, kaons
Are protons leptons or hadrons (if hadrons, which type)?
Hadrons, and a baryon
Are neutrons leptons or hadrons (if hadrons, which type)?
Hadrons, and a baryon
Are electrons leptons or hadrons (if hadrons, which type)?
Leptons
Can pions/ π mesons be charged?
Yes, positively π+, negatively π- and no charge π^0
What are the rest masses of pions?
Between muon and proton. About 300x electron
Are pions unstable, and which decay do they interact with?
Very unstable, interact through weak interaction
What does π+ decay into?
Anti muon and neutrino
What does π- decay into?
muon and anti-neutrino
What does π^0 decay into?
2 high energy photons
Are pions leptons or hadrons (if hadrons, which type)?
Hadrons, mesons
Can kaons/ K mesons be charged?
Yes, positively K+, negatively K- and no charge K^0
What are the rest masses of kaons?
Greater than pions, but less than a proton
Are kaons unstable, and which decay do they interact with?
They are unstable, and interact through weak interaction far more slowly than pions
Why are kaons called strange particles?
Due to slow rate of decay 10^-10s - unexpected
What do kaons decay into?
Pions, muons and neutrinos
What are fundamental particles and give an example
Particles that do not decay into any other particles except leptons. e.g leptons
What are the 3 families of leptons?
1 - Electrons, electron neutrinos
2 - Muon and muon neutrinos
3 - Tau and tau neutrinos
what is the charge of muons? (μ-)
Negative
How big in size are muons in relation to electrons?
200x more massive
What is the antiparticle of muons and give the charge
Antimuons (μ+) Positively charged
What do muons decay into through which type of interaction?
Decay via weak interaction into electrons and anti neutrinos
What do antimuons decay into?
Positrons and neutrinos
What must all interactions conserve?
Energy, charge, lepton number + type, baryon number and strangeness (strong interaction only)
What are sigma particles?
Baryons with a strangeness of -1
What is strangeness?
Property of some hadrons due to slow interactions with others
Strangeness of K- meson?
-1
Strangeness of K+ meson?
+1
Strangeness of K^0 meson?
-1
