Particles Flashcards
What is the SNF
Fundamental force, keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons
State a use of radioactive isotopes
Carbon Dating - the amount of carbon 14 in a material can be used to estimate its age
What is the range of the strong nuclear force
Repulsive : <0.5 fm
Attractive: 0.5-5 fm
negligible: >3 fm
what makes a nucleus unstable
Too many protons or nuetrons or both that means the SNF and Elctrostatic force do not balance
how do nuclei with too many neutrons decay
Beta minus
how do nuclei with to many nucleons decay
Alpha decay
What exchange particle is used in beta minus decay
W minus boson
How was the exitance of the neutrino hypothesized
- Energy before and after beta minus decay was no conserved therefore another particle had to exist to which this energy was transfered too
how does a nuclei decay with too many Protons
Beta plus decay
what is an antiparticle
particle with the same rest energy and mass but all other properties are opposite
what particles have antiparticles
every particle
What is the antiparticle of a pion 0
pion 0
what is annihilation
When particle and its antiparticle meet the mass + KE of the particles is converted into 2 gamma rays which go in opposite directions to conserve momentum
what is pair production
photon is converted into equal matter and antimatter. Photon energy must be greater or equal to than the total rest energy of both particles.
Excess photon energy is converted to kinetic energy of particles
what are the exchange particles and ranges of the four fundamental forces
- SNF - Pion - 3 fm
- WNF - W boson - x10-18
- EM - Virtual photon - infinite
- Gravity - Graviton - infinite
Name the two mesons
Pions, Kaons
what is a hadron
Hadrons are particles made of quarks that experience the SNF. They consist of Baryons and Mesons
what is the quark structure of mesons
quark - antiquark pair
Property’s conserved in particle interactions
Energy
charge
baryon number
lepton number
momentum
when is strangeness conserved
during the SNF
what is the exchange particle for Beta plus decay
W plus boson
what is electron capture
An electron is absorbed into the nucleus of an atom
what is the exchange particle for electron proton collision
w minus boson
what is electron capture
electron is absorbed into the nucleus
what is the exchange particle for electron capture
W + boson
what does a muon decay into
electron and two types of nutrino
what types of neutrino are produced when a muon decays
anti electron neutrino
muon neutrino
what do the baryon and lepton numbers symbolize
+1 - baryon/lepton
-1 - anti baryon/lepton
0 - not baryon/lepton
how are strange particles produced and how do they decay
They are produced during the strong interaction and decay via the weak interaction
How much can strangeness change during the strong interaction
0, -1 or +1
what makes kaons different
they are strange
what are leptons
Fundamental particles that do not experience the Strong interaction
what is significant about a proton
it is the only stable baryon
what particle does a kaon decay into
pion
what particles do the strong and weak force act on
Hadrons
All particles
How does EM radiation travel
EM radiation travels in high energy packets called virtual photons
when does the WNF occur
when there is a change in quark character
what is a quark
fundamental particle that makes up hadrons
what is the photoelectric effect
elections are emitted from the surface of a metal after light above a threshold frequency is shone on the metal
- what is the threshold frequency
The minimum frequency of light required for electrons to be emitted, it is different for all metals
why does the wave theory of light not explain the photoelectric effect
It would suggest any frequency of light could cause the photoelectric effect as the energy absorbed by the electrons would increase with each oncoming wave of light
Photoelectrons are emitted instantly and only at certain frequency’s therefore the wave theory of light doesn’t work
How does the particle model of light explain the photoelectric effect
- energy is not transfered continously, electron absorb descrete energys
- intensity only increases the number of photoelectrons not wether the effect occours
what effect does frequency and intensity have on the photoelectrons
- if frequency is increased each photon will have more energy
- if intensity is increased there is more photons per second therefore if there energy is above threshold frequency more photoelectron will be emitted
what happens when a photon of energy above threshold frequency is absorbed by electrons
some energy is transfered to overcoming the work function (breaking metalic bonds) then excess energy is converted to kinetic
What is the work function of a metal
- minimum energy for an electron to escape metallic bonding/be liberated from the surface of the metal
what is the stopping potential
P.D across a metal required to stop photoelectrons with maximum kinetic energy from being liberated
what can be measure by finding the stopping potential
- Maximum kinetic energy
what is the equation for the maximum kinetic energy of a photoelectron
Charge x stopping potential
what is excitation
when an electron in a discrete energy level experiences a collision with another particle and gains energy causing it to move up to a higher energy level
What is ionization
When an electron gains enough energy from a collision to be liberated from the atom
what is ionization energy
Minimum energy for an electron to be liberated
What happens after Excitation
Electron returns to its original energy level releasing the energy it gained in the form of a photon
How does a florescent tube work
- High voltage applied across mercury vapor that accelerates free electrons causing them to collide with mercury electron therefore exciting the mercury electrons
- Mercury electrons deexcite releasing a UV photon that is absorbed by Phosphorus coating on florescent tube causing Phosphorus electrons to excite and deexcite releasing a visible light photon
what is an electron volt
energy gained by 1 electron when passing through a potential difference of 1 volt
How to convert Ev to Joules
x 1.6x10-19
what can be used as evidence for discrete energy levels in atoms
-Line emission and absorption spectrum
- on these spectrums lines appear at specific wavelengths showing electrons can only absorb or give off exact energy’s to be excited to higher levels
how do you create a line emission spectrum
by passing light from electrons that have been excited/deexcited through a diffraction grating/prism to separate the wavelengths.
how do you create a line absorption spectrum
By passing white light through an excitable sample then through a diffraction grating/prism.
how can you find energy level differences in specific atoms
Use there emission or absorption spectra to analyze specific wavelengths and find the energy differences
what is wave particle duality
All particle can be shown as having wave and particle properties
what wavelength does gamma have
<x10^-12
why must the virtual photon exist and why cant it be detected
- it must exist as EM radiation does not act instantly it takes time to act over e certain distance meaning the particle must travel in between
- if it was to be detected then the detector would technically block the interaction from taking place as it would absorb the virtual photon, because the em interaction always takes place it is impossible for the particle to be detected
