Particles And Radiation Flashcards
What is the charge of a proton and electron?
+ or - 1.60x10^-19
What is the mass of a proton?
1.673x10^-27 kg
What is the mass of a neutron?
1.675x10^-27 kg
What is specific charge?
Charge per unit mass
To work out : Charge(C)/ Mass(kg)
What is an isotope?
Atoms of an element with the same number of protons and a different number of neutrons
What is the strong force?
A force that acts between nucleons in a nucleus to keep it stable. It is attractive at distances of up to 3fm and repulsive at separations less than 0.5fm
What makes a nucleus unstable?
Nuclei which have too many of either protons or neutrons or both
How do nuclei with too many nucleons decay?
Alpha decay
How do nuclei with too many neutrons decay?
Beta minus decay in which a neutrons decays into a proton by the weak interaction
How was the existence of the neutrino hypothesised?
The energy of particles after beta decay was lower than before, a particle with 0 charge and negligible mass must carry away this excess energy, this particle is the neutrino
What is meant by beta minus decay?
When a neutron turns into a proton, the atom releases an electron and an anti-electron neutrino
What occurred when a particle and antiparticle meet?
Annihilation:
The mass of the particle and antiparticle is converted back to energy in the form of 2 gamma ray photons which go in opposite directions to conserve momentum
What is pair production?
A gamma ray photon is converted into a particle-antiparticle pair
What is an eV?
The amount of energy, that an electron gains when it undergoes a potential difference of 1volt, which is 1.60x10^-19
Name the 4 fundamental forces?
•Gravity
•Electromagnetic
•Weak nuclear force
•Strong nuclear force
What is the exchange particle for electromagnetic force?
The virtual photon
What are hadrons?
A subatomic particle that is made up
Of quarks and experiences the strong nuclear force
What is the exchange particle of the weak nucleus force?
The W boson ( W+ or W-)
When does the weak nuclear interaction occur?
When a quark changes into another quark
Which properties must be conserved in particle interactions?
•Energy
•Charge
•Baryon number
•Lepton number
•Momentum
•Strangeness(only for strong interaction)
What are the classes of hadrons?
•Baryons(three quarks)
•Mesons(1quark, 1antiquark)
Pion and kaon are both examples of which class of particle?
Mesons
The pion can be an exchange particle for which force?
The strong nuclear force
What is the difference between a gluon and a pion?
Gluons are only the mediators of strong force between quarks inside protons or neutrons. Pions are actually the mediators between protons and neutrons.
What is a kaon made up of?
1 up quark, 1 down quark and 1 strange quark
What particle does a kaon decay into?
A kaon decays into a pion
What are baryons?
They are heavy subatomic particles that are made up of three quarks
Give some example of baryons?
•Proton - uud
•Neutron - ddu
What is a significant about a proton?
*It is the only stable baryon
*All baryons will eventually turn into protons
What are some examples of leptons?
•Electrons
•Muon
•Neutrino
•the antiparticles of the above
What does a muon decay into?
An electron
What is the strangeness value of a strange quark?
-1
Complete the sentence:
Strange particles are produced through__________ and decay through __________.
•Strong interaction
•Weak interaction
When does photoelectric emission take place?
When the frequency of the electromagnetic radiation is above the threshold frequency
What can the wave theory of light not explain?
•the existence of the threshold frequency
•why photoelectric emission occurs without delay
What did Einstein assume?
That light is composed of wave packets (or photons)
Give the equation for the energy of a photon
Energy of photon = h x f
When can an electron leave a metal’s surface?
•If the energy gained from a single photon exceeds the work function of the metal
•This is the minimum energy needed by an electron to escape from the metal surface
What is the excess energy of the photoelectron turned into?
Kinetic energy
What is a photoelectron?
An electron emitted from a substance due to the photoelectric effect
What is the equation for the maximum kinetic energy of an emitted electron?
Ekmax =hf - Φ
What is the stopping potential?
The minimum potential needed to stop photoelectric emission
